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Email deliverability
Email deliverability is whether your message reaches the recipient's inbox, not just whether the receiving server accepted it.
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Start with the failure you have.
Run the deliverability test →The six most common ways mail fails, each with the exact fix.
Why is Microsoft 365 rejecting my email with a 550 5.7.x error?Microsoft 365 returns 550 5.7.x when your mail fails a policy or authentication check. Fix SPF, DKIM, and DMARC alignment to clear the access-denied bounce.
What does SMTP error 421 mean and how do I fix it?SMTP error 421 is a temporary deferral, not a bounce. Fix it by slowing your send rate and authenticating mail with SPF, DKIM, and DMARC before retrying.
Why do my emails land in Gmail's Promotions tab?Why emails land in Gmail's Promotions tab: classify the delivered message, test one sender-controlled change, and validate the same sending path.
Why is Gmail rejecting my emails with a 550 error?Gmail 550 5.7.26 rejections mean your mail fails authentication. See why Google now rejects instead of defers, and the exact fixes to get delivered.
Why is Yahoo blocking my emails as unauthenticated?Yahoo blocks unauthenticated mail because SPF, DKIM, or DMARC failed. Fix the 550 5.7.9 'sender is unauthenticated' bounce by authenticating and aligning.
Why is my email queued and how do I fix it?Why is my email queued? Find the queue location, capture the SMTP response, repair the documented condition, and validate the same delivery path.
What decides inbox placement
| Factor | What it is | What it looks like when it breaks |
|---|---|---|
| Authentication | SPF, DKIM and DMARC prove the mail is really from your domain, and that the passing domain aligns with the visible From address. | Hard rejections: 550 5.7.26 from Gmail, 550 5.7.515 from Outlook.com. |
| Reputation | How mailbox providers rate your sending domain and IP based on history: complaint rates, spamtrap hits, bounce rates, blocklist presence. | 4xx deferrals and spam placement even when DNS is perfect. |
| Engagement | Whether recipients open, reply and want the mail, and what the message itself looks like to a filter. | The Promotions tab, then the spam folder, as engagement decays. |
Authentication proves who sent the message. Publish SPF, sign with DKIM, and set a DMARC policy so the passing domain aligns with your visible From address. Gmail and Yahoo have required this of bulk senders since February 2024. Microsoft added the same requirement for Outlook.com: its postmaster page says non-compliant mail goes to Junk with rejection to follow, and its April 2025 announcement said rejection with 550 5.7.515 would apply from 5 May 2025.
Reputation is how mailbox providers rate your sending IP and domain based on history: complaint rates, spamtrap hits, bounce rates, and whether your IP has landed on a blocklist. A damaged reputation shows up as 4xx deferrals and spam placement even when your DNS is perfect, and it recovers slowly. Providers want to see weeks of a low complaint rate before restoring full placement.
Engagement decides the last mile: which tab you land in and whether you stay out of spam over time. Authentication is necessary but not sufficient: it establishes that you are who you claim to be, and reputation and engagement decide whether that trusted sender reaches the inbox.
When the problem is ongoing rather than a one-off test, the Palisade Email Deliverability Platform connects those signals to real DMARC report traffic, names the sending service behind an authentication failure, and opens the remediation work with the evidence attached.
Delivery vs deliverability
Email delivery and email deliverability get used interchangeably and mean different things. A server accepting a message only means it was not rejected outright; the message can still be filed as spam, quarantined, or dropped into a tab nobody reads. You can have perfect delivery and poor deliverability at the same time, every message accepted, every message in spam. Deliverability is the outcome that matters: the mail lands where it can be seen and acted on.
| What it measures | What 100% looks like | |
|---|---|---|
| Delivery | The receiving server accepted the message instead of bouncing it. | No bounces, but the mail may all be sitting in spam. |
| Deliverability | The message reached the inbox specifically, not the spam folder. | The mail is where the recipient will actually see it. |
The bulk sender requirements
Gmail, Yahoo and Outlook.com apply a shared baseline to anyone sending at volume. Non-compliant bulk mail is rejected rather than quietly filtered, so these are gating requirements, not best-effort suggestions.
| Requirement | Threshold | Enforced by |
|---|---|---|
| SPF and DKIM published, with one aligned so DMARC passes | Required; p=none is an acceptable start | Gmail and Yahoo since February 2024; Outlook.com since May 2025 |
| Spam complaint rate | Below 0.3%, with 0.10% the recommended target | Google Postmaster Tools |
| One-click unsubscribe on marketing mail (RFC 8058) | Honoured within two days; transactional mail exempt | Gmail and Yahoo |
| Valid forward and reverse DNS, plus TLS on the connection | Required | All three providers |
| Volume that triggers the strict thresholds | About 5,000 messages a day to one provider's users | Gmail and Outlook.com; Yahoo declines to publish a number |
How to improve email deliverability
Improving deliverability means fixing three things in order: authentication first, then reputation, then engagement. Skipping to content changes while authentication is broken is the most common wasted effort.
- Authenticate every sending servicePublish SPF, sign with DKIM, and set a DMARC policy. Every tool that sends as your domain, CRM, invoicing, help desk, needs to be covered, not just your mail server.
- Align the passing domain with your From addressDMARC only passes when SPF or DKIM authenticates the same domain the recipient sees. A passing SPF check on a vendor's domain does not help you.
- Move off p=noneStart at p=none with an aggregate-report address so you can see every source sending as your domain, then tighten to quarantine and reject once the reports confirm your legitimate mail passes.
- Keep the complaint rate under 0.10%Send only to people who opted in, and make unsubscribing easy. 0.3% is where mitigation starts, not a safe operating level.
- Clean the listRemove hard bounces immediately and drop addresses that have not engaged in months. Spamtraps and invalid addresses do more damage than a smaller list does.
- Warm any new domain or IP graduallyA cold sender with no history has no reputation to draw on. Increase volume steadily and keep the pattern consistent rather than spiking.
- Check the sending IP against the major blocklistsA listing explains sudden 5xx rejections that authentication changes will not fix. Delist through the operator's own process.
- Monitor DMARC reports continuouslyA broken sender should show up in a report, not in lost mail. Aggregate reports are how you find the shadow sender before a customer does.
Fix delivery to a specific provider
Why are my emails being blocked?
Emails get blocked for four main reasons: your domain fails SPF, DKIM, or DMARC checks, your spam complaint rate crossed the provider's threshold, your IP or domain sits on a blocklist, or you broke a bulk-sender rule. Read the bounce to identify the provider, fix authentication first, then check blocklists and complaint data.
Why is Outlook blocking my emails?
Outlook blocks outbound mail for three reasons: your domain fails SPF, DKIM, or DMARC checks; your sending IP or domain has a poor reputation with Microsoft's SmartScreen filter; or your IP sits on a Microsoft block list. Fix authentication first, then check SNDS and request delisting; most blocks trace back to those three.
How to stop emails going to spam in Outlook
To stop emails going to spam in Outlook, fix the four things Microsoft's filter actually scores: authentication that passes but doesn't align with your From domain, a rising junk-complaint rate, weak list hygiene and content signals, and a cold IP or domain with no sending history. Align SPF and DKIM first; that is the post-May-2025 junk trigger.
Why do emails go to junk in Hotmail and Outlook?
Emails go to junk in Hotmail and Outlook.com when Microsoft's SmartScreen filter distrusts the sender: missing or misaligned SPF, DKIM, or DMARC, a high junk-complaint rate, a new IP with no history, or a stale mailing list. Since May 2025, Microsoft's high-volume sender requirements make failing authentication a documented enforcement trigger: Junk placement first, then rejection. Fix authentication first; reputation follows.
Why does Outlook move emails to junk after they arrive?
Outlook moves delivered mail to Junk after arrival for four main reasons: Microsoft's zero-hour auto purge (ZAP) re-scans the last 48 hours of delivered mail against updated spam and phishing signatures; the recipient marked you as junk, so every future message is classified as spam; the Outlook desktop client's own junk filter re-files it; or a recipient rule moves it. Authentication and complaint rate decide the first two.
Why is Microsoft 365 blocking outbound emails?
Microsoft 365 blocks outbound mail for three reasons: a user or connector exceeded outbound sending limits and landed on the Restricted entities page; Exchange Online classified the mail as spam and routed it through the high-risk delivery pool; or the tenant hit Exchange Online's service limits. Recipient-side rejections trace to missing SPF, DKIM, or DMARC.
Why is Microsoft blocking my automated emails?
Microsoft blocks automated mail (scanners, CRMs, monitoring alerts) for three reasons: the app or device fails SPF and DKIM alignment for your domain; it uses a submission method the tenant no longer accepts, like Direct Send or Basic-auth SMTP; or it trips Exchange Online throttling. The Office 365 mail filter treats unauthenticated app mail as anonymous internet traffic.
Why are my emails going to spam in Gmail?
Gmail spam-folders outbound mail for four main reasons: SPF, DKIM, or DMARC is missing or unaligned under Google's Email sender guidelines; your user-reported spam rate crossed 0.3%; your domain reputation in Google Postmaster Tools is Low or Bad; or you send bulk mail without one-click unsubscribe. Fix authentication first; everything else builds on it.
Why does Gmail mark new domain emails as spam?
Gmail spam-folders mail from a new domain because the domain has no sending history, so authentication and behavior are the only signals Google can score. Missing SPF, DKIM, or DMARC, a cold start at full volume, and a bare domain with no web presence all read as spam. Authenticate everything first, then warm up gradually.
Your email has been blocked because the sender is unauthenticated: the Gmail fix
Gmail returns "blocked because the sender is unauthenticated" when a message passes neither SPF nor DKIM for your domain. Under Google's February 2024 sender requirements, unauthenticated mail is spam-foldered or, as here, refused outright. The fix is DNS: publish SPF and DKIM for every service that sends as your domain, confirm both pass and align, then re-send.
Why is Yahoo blocking my emails?
Yahoo blocks outbound mail for three main reasons: your domain fails SPF, DKIM, or DMARC under the sender requirements Yahoo has enforced since February 2024; your spam complaint rate is above Yahoo's published 0.3% ceiling; or your IP has a poor reputation or sits on a blocklist Yahoo consults. AOL runs on the same filters, so one fix clears both.
Why is iCloud blocking my emails?
iCloud Mail blocks outbound mail for three main reasons: your sending IP is flagged by Proofpoint's reputation system (a linkage neither vendor documents, but one deliverability teams widely report in iCloud bounces), your domain fails SPF, DKIM, or DMARC, or your stream breaks one of Apple's published bulk-sender rules. Fix authentication first, check the IP at Proofpoint's lookup, then escalate to Apple's postmaster address.
Questions, answered straight
What is a good email bounce rate?
Under 1% is healthy, 2% needs investigating, 5%+ is an emergency. The bounce-rate benchmarks ESPs actually publish, plus the triage table to fix yours.
Why are my Mailchimp emails going to spam?
Mailchimp campaigns landing in spam? The four real causes: unauthenticated sending domain, shared IP reputation, list decay, engagement. And the DNS fix.
How to authenticate email for marketing
The platform-agnostic setup order: sending subdomain, SPF include, custom DKIM, DMARC with rua, alignment check, policy ramp. With live ESP doc links.
What is SPF flattening?
SPF flattening swaps include: mechanisms for raw IPs to beat the 10-lookup limit. When it helps, when it silently breaks, and the alternatives that age better.
Why are my newsletters going to spam?
Four causes: failed SPF/DKIM/DMARC, no one-click unsubscribe, complaints over 0.3%, dead engagement. What Gmail and Yahoo actually require, plus the fix.
What is Google Postmaster Tools?
Google Postmaster Tools explained: the v2 dashboards, DNS TXT setup, the 0.3% spam-rate line, and how to read it before moving DMARC to p=reject.
What is Microsoft SNDS?
SNDS is Microsoft's free per-IP reputation portal for Outlook.com senders. What it shows, how to sign up, its limits, and how it pairs with DMARC reports.
What are DMARC aggregate reports?
Daily XML files sent to your rua address: every source IP, message counts, disposition, SPF/DKIM results. What's inside one and how to read it.
Why is DMARC failing but SPF passes?
SPF checks the Return-Path domain; DMARC needs it to match your From domain. Why ESP bounce domains, forwarding, and strict aspf break alignment.
How do I move from DMARC p=none to p=reject?
The RFC 9989 playbook from p=none to p=reject: monitor with rua, fix alignment, test full quarantine on lower-volume subdomains, then enforce.
Does DMARC affect email marketing?
Yes. Google and Microsoft require DMARC for bulk senders, misalignment sends campaigns to spam, and enforcement unlocks your BIMI logo in the inbox.
Why did my email get clipped in Gmail?
Gmail clips HTML over ~102KB behind a View entire message link. What counts toward the limit, why it hurts opens and unsubscribes, and how to slim the template.
The other 85 deliverability guides
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Reverse DNS and email spam: what PTR checks really meanReverse DNS email spam checks use PTR records as one sender signal. Learn what Google requires, what receivers may do, and how to validate it.
Ways to improve email deliverabilityWays to improve email deliverability start with evidence from the sending path and mailbox provider, not unsupported email rules, with documented evidence.
AI email warmup: what it is and what it cannot proveAI email warmup automates messages and mailbox interactions to try to improve sender reputation, but it cannot prove inbox placement or email.
Bounce email addressBounce email address explained: identify the envelope return path, read delivery-status evidence, repair the confirmed cause, and retest the same route.
Brevo email warmupBrevo email warmup is not documented as a native Brevo feature in the available help material. Check domain authentication before changing sending.
Cheap email warmup: how to evaluate the offerCheap email warmup is only worth considering when its testing, mailbox coverage, account handling, and limits match evidence from your real sending.
Check email address deliverabilityCheck email address deliverability by verifying address, MX, and mailbox signals, then separate valid results from actual inbox placement today.
Email IP warmupEmail IP warmup is a sending-infrastructure practice offered by some email platforms. Check authentication and delivery evidence before attributing a.
Email list bounce checker: how to interpret and act on resultsEmail list bounce checker results help separate bad, deliverable, and uncertain addresses before sending, then guide list cleanup and retesting.
Email warmup by GMass: what the public site confirmsEmail warmup by GMass is not documented on GMass's public homepage. See what GMass confirms and what to check before sending campaigns safely.
Email warmup company: how to assess oneEmail warmup company services connect mailboxes for message exchanges or simulated activity. Assess their diagnostics, data handling, and claims.
Email warmup GitHub: what the search does and does not showEmail warmup GitHub does not identify a verified GitHub warmup feature. Check the actual sending domain's authentication and security evidence.
Email warmup reviews: what vendor claims can proveEmail warmup reviews should compare documented controls and independently test placement, because vendor claims alone cannot prove deliverability results.
Emailchaser email warmupEmailchaser email warmup gradually ramps up new mailboxes, according to Emailchaser. Learn what that claim covers and what it cannot prove here.
Gmail bulk sender guidelinesGmail bulk sender guidelines: meet Gmail's 5,000-message threshold with SPF, DKIM, DMARC, TLS, alignment, unsubscribe, and validation for senders.
Gmail one-click unsubscribe requirementsGmail one-click unsubscribe requires bulk senders to add signed headers, an HTTPS POST endpoint, and a visible body link for eligible Gmail messages.
GoHighLevel email warmup: how the fixed-stage model worksGoHighLevel email warmup uses fixed sending stages for eligible LC Email dedicated domains. Learn what it controls and how to validate mail.
Google email warmup: what it is and what Google does not defineGoogle email warmup is an industry practice, not a Google-published process. Separate vendor claims from authentication and deliverability checks.
Google Postmaster domain and IP reputation dashboardGoogle Postmaster domain and IP reputation dashboards are legacy views being retired in v2. Learn what their ratings mean and what to check next.
How to improve HubSpot email deliverabilityHubSpot improve email deliverability by checking sender authentication, message results, and list signals before changing campaign practices.
Is one-click unsubscribe mandatory?Is one-click unsubscribe mandatory? Gmail requires it for qualifying bulk marketing and subscribed mail. Learn the scope, dates, headers, and checks.
Lemlist email warmup: what Lemwarm does and cannot proveLemlist email warmup uses Lemwarm to send warm-up activity and track deliverability signals, but its score alone does not prove inbox placement.
Lemwarm email warmupLemwarm email warmup exchanges emails through its network and reports a daily score. Learn what its score can indicate and what to verify separately.
Mailchimp email warmup: what is documentedMailchimp email warmup is not a documented Mailchimp workflow in available official evidence. Check authentication and sending evidence instead.
Mailshake email warmupMailshake email warmup is a built-in deliverability tool, but it does not replace SPF, DKIM, DMARC, list quality, or real sending-path checks.
N8n email warmup: what n8n can and cannot doN8n email warmup can automate parts of an email workflow, but the available n8n documentation does not establish n8n itself as an email-warmup service or.
Open source email warmup: what the term actually meansOpen source email warmup is not a defined software category. Learn how to distinguish open-source email infrastructure from documented warm-up tools.
Reply.io email warmup: what it does and cannot proveReply.io email warmup starts when you connect a mailbox and tracks warmup activity, but it does not prove inbox placement or instant outreach readiness.
Sender reputation in email marketingSender reputation in email marketing is an assessment of how mailbox providers may view a sender. Learn what it can show and how to check it.
SendGrid email warmup: what you can verify firstSendGrid email warmup needs current provider guidance. Verify your sending path and email authentication before adopting a ramp schedule for your account.
Smartlead email warmupSmartlead email warmup simulates opens, reads, and replies, but it does not replace checking SPF, DKIM, DMARC, or real delivery results today.
Unlimited email warmup: what the label actually coversUnlimited email warmup usually describes a vendor plan feature, not unlimited sending. Compare the stated inbox, support, test, and daily-email limits.
Warmly email warmup: what the search term may meanWarmly email warmup is an ambiguous search term. It may refer to Warmy Email Warm-Up, but the spelling and intended workflow are not confirmed.
What causes an email to bounce?What causes an email to bounce? Preserve the bounce evidence, validate undeliverable addresses, correct list data, and retest the same path.
What is a good email deliverability rate?What is a good email deliverability rate? No universal percentage is reliable. Assess delivery, inbox placement, and provider results over time.
Which domain reputation statement is correct?Which statement about domain reputation is correct? It reflects observed harmful activity and can change as internet activity changes over time.
Which strategy will improve email deliverability?Which strategy will improve email deliverability? Start by identifying the evidence behind delivery issues, then prioritize the control your team can.
Why emails go to spam instead of inbox GmailWhy emails go to spam instead of inbox Gmail: the Spam folder alone cannot identify the cause. Use message and sender evidence to investigate.
Woodpecker email warmupWoodpecker email warmup is a free feature Woodpecker says automatically builds sender reputation. Learn what it covers and what to check separately.
Zoho email warmup: what it is and what it cannot proveZoho email warmup is an optional third-party workflow, not a proven Zoho requirement. Check domain authentication before connecting a warm-up service.
Why are my emails landing in spam and how can I fix it?Why are emails landing in spam? Inspect the delivered message, verify aligned SPF, DKIM, and DMARC, then retest the exact sending path after each repair.
Check the Spamhaus blacklist: identify and fix a listingCheck the Spamhaus blacklist, identify the listed IP or domain, follow the correct remediation path, and validate a clean sending result safely.
Does email warmup work?Does email warmup work? A gradual ramp of authenticated real mail can help, but it cannot prove inbox placement or replace direct sender evidence.
One-click unsubscribe law: what RFC 8058 actually requiresOne-click unsubscribe law: RFC 8058 is an IETF technical standard that Gmail and Yahoo enforce as a bulk-sender requirement, not a US statute.
How to check and improve your email domain reputationHow to check email domain reputation: assess public signals, authentication, provider evidence, and DMARC reports before making safe delivery changes.
Best email deliverability service: choose the right category firstBest email deliverability service options depend on the problem: compare DMARC, inbox placement, list validation, consulting, and ESP categories.
What is an email warmup API?An email warmup API controls a provider's warmup process. Learn what its status can show and which production evidence it cannot replace.
Email warmup appsumoAppSumo's Email Warmup listing is sold out. Learn what its historic claims mean and what to check on a real sending path.
Email warmup schedule: a controlled ramp for real mailUse an email warmup schedule as a controlled ramp for real mail, with evidence for when to hold, advance, or investigate.
Microsoft SMTP 5.4.1 Relay Access DeniedDiagnose Microsoft SMTP 5.4.1 Relay Access Denied from the full NDR. Identify the rejecting host, check destination acceptance and connectors, then retest.
Inbox placement test: what it shows and what it cannot proveInbox placement test results show how a sample email reached seed mailboxes at one time, plus the evidence needed before changing a campaign.
Instantly email warmupInstantly email warmup uses pool-based message activity and a Health Score, but it does not prove campaign authentication or inbox placement.
Mailgun email warmup: when to warm a dedicated IPMailgun senders on shared IPs do not need new-IP warmup. Learn when a new dedicated IP needs a controlled ramp and what to verify.
Soft bounce vs hard bounce: what each means and what to doSoft bounce vs hard bounce: learn the temporary and permanent delivery difference, how ESP labels vary, and how to respond safely with evidence.
What is a domain reputation?Domain reputation is a mailbox provider's assessment of a sending domain. Learn which signals you can check, what providers keep private, and how to.
Why Mailchimp email goes to spam after marked deliveredWhy Mailchimp email goes to spam after marked delivered: separate accepted delivery from mailbox placement, inspect headers, and retest safely.
Yahoo bulk sender requirementsYahoo bulk sender requirements: authentication, DMARC alignment, unsubscribe, complaint-rate, DNS, and validation checks for Yahoo Mail senders.
How do you authenticate an email for Gmail?Authenticate email for Gmail with SPF, DKIM, and DMARC, then validate the exact sending path in Gmail headers and DMARC reports, and verify sender paths.
Google's stricter email sender rules (Nov 2025)Google's stricter email sender rules: track Gmail's authentication, alignment, TLS, DNS, spam-rate, and unsubscribe requirements after Nov 2025.
What are the best email verification tools?What are the best email verification tools? Compare syntax, DNS, mailbox, and list-validation checks with their deliverability limits before you send.
What is an email blocklist and how do you check one?A blocklist flags an IP a DNS-based list has linked to spam. Learn how blocklisting works and how to check if your mail server is blocklisted.
Email bounce rate: how to calculate and investigate itEmail bounce rate is bounced messages divided by your ESP's stated denominator. Separate hard and soft bounces, inspect reasons, and retest.
Email sender reputationEmail sender reputation is how mailbox providers may assess a sending IP address or domain as reputable or spam-related. Learn how to investigate it.
How do Exchange Online sending and receiving limits work?Exchange Online sending and receiving limits use separate recipient, message, mailbox, and tenant counters. See which limit applies and how to verify it.
How do you warm up a new sending domain safely?Warm up a new sending domain safely by authenticating mail first, increasing wanted mail gradually, and pausing when delivery signals worsen.
How Palisade DMARC monitoring protects email deliverabilityPalisade DMARC monitoring helps protect email deliverability by finding unauthenticated sending sources before a stricter DMARC policy is requested.
Test email reputationTest email reputation with a public domain check, interpret blocklist findings, collect message evidence, and retest after a documented repair.
What is an IP reputation?IP reputation is a receiving provider's assessment of an email-sending IP. See what affects it, its limits, and how to investigate delivery.
What is Microsoft's equivalent to Google Postmaster Tools?Microsoft's equivalent to Google Postmaster Tools is SNDS plus JMRP for Outlook.com consumer-mail data, with important limits, for Outlook.com.
Apollo email warmup: what it does and what it cannot proveApollo email warmup uses inbox-network activity for connected mailboxes, but it does not prove authentication, consent, or inbox placement today.
Email warmup software: how to evaluate your optionsEmail warmup software can simulate inbox activity, but choose it only after verifying its scope, claims, controls, and deliverability tradeoffs.
Is Gmail filtering my emails? How to tell and fix itIs Gmail filtering your emails? Learn how to tell spam-foldering from a bounce or the Promotions tab, and the exact authentication and reputation fixes.
What is an email spam bot and how do you stop one?Spam bots harvest addresses and send at scale, often forging your domain to do it. How they operate, and the authentication that stops them using your name.
Why would an email bounce?Why would an email bounce? Preserve the original delivery notice, identify the sending path and provider, then use provider evidence to choose a repair.
Bounce-back email: how to read the error and fix the causeBounce-back email errors identify a delivery failure. Read the SMTP status, repair the confirmed cause, and retest the same sending path now.
Email warmup service: compare the evidence before choosingEmail warmup service comparison: assess MailToaster, verify what other vendors document, and separate warm-up claims from authentication checks.
MxToolbox email deliverability tool: run and interpret a reportMxToolbox email deliverability tool: send a test message, interpret the report, choose the supported next check, and retest the same path now.
Warmy email deliverability testWhat a Warmy deliverability test measures, how to read its placement result, and the evidence to confirm before changing a sender's configuration.
Why is my email going to spam in Outlook but not Gmail?Mail lands in Outlook spam but not Gmail because Microsoft weighs IP reputation and its own authentication rules differently. Here's how to diagnose and fix it.
Why am I not receiving emails? How to troubleshootNot receiving emails? Work through spam filters, a full mailbox, forwarding loops, MX records, and blocklists, the fixes that recover missing mail fast.
What are Microsoft's new email authentication rules?Microsoft announced it will enforce the same email authentication standards that Google and Yahoo already require.
What can we learn from Will Boyd about deliverability?Deliverability expert Will Boyd on permission, data, and explaining DMARC simply, plus how those lessons translate into authentication that reaches the inbox.
What Can We Learn from Travis Hazlewood About Email Deliverability?Travis leads email deliverability at Ortto, bringing five years of cross-platform experience to keep both platform and customer emails landing in inboxes.
What does BCC mean in email?Learn what BCC means in email and how it protects privacy.
Look up an exact answer
Diagnose your domain
Send a message to the Email Spam Checker to see what the receiving server recorded and why it may be filtered. For the DNS side, run a free Email Security Score or check a sending IP against the major blocklists.
Sources
- Google's sender guidelines require keeping the spam rate reported in Postmaster Tools below 0.3%, and recommend staying below 0.10%. Google: Email sender guidelines, checked 2026-07-20.
- Yahoo publishes the same baseline for bulk senders: authentication, a low complaint rate, and one-click unsubscribe. Yahoo Sender Best Practices, checked 2026-07-20.
- One-click unsubscribe on marketing mail is specified by RFC 8058. The two-day window for honouring it is Google's and Yahoo's requirement, not the RFC's. RFC 8058, checked 2026-07-20.
- Microsoft's announcement said Outlook.com would reject high-volume mail failing SPF, DKIM or DMARC with 550 5.7.515 from 5 May 2025; the live postmaster page describes Junk placement with rejection to follow. Microsoft Support: NDR 550 5.7.515, checked 2026-07-17.