Find why business email went to spam, bounced or was blocked

Start with the failed message and the system that sent it. The guides below help you use bounces, headers, DMARC results and provider responses to narrow the cause before changing DNS.

People reviewing information on a laptop screen.

Email went to spam

Check whether the pattern affects one provider, message type, sending platform or recent change.

Find why legitimate email reaches spamSeparate authentication, reputation, content, permission and sending-pattern causes. Fix Gmail 550 5.7.26 rejection evidenceRead the exact Gmail response and check the authentication result it identifies. Investigate a sudden delivery dropCompare recent DNS, sending, content and infrastructure changes without changing everything at once.

SPF or DKIM passed, but DMARC failed

An authentication pass only helps DMARC when the authenticated domain aligns with the visible From domain.

What is DMARC? A plain-English guide to stopping email spoofing of your domainWhat is DMARC and what does it stop? Plain-English guide to SPF and DKIM alignment and policies, so you block exact-domain spoofing without losing legitimate mail. SPF passes but DMARC failsTrace the envelope domain and compare it with the visible From address. DKIM passes but DMARC failsCheck which domain signed the message and whether that signature aligns. Understand DMARC alignmentSee why an authenticated third-party route can still fail the domain check.

Email was accepted but did not reach the inbox

Delivery, inbox placement and seed-test results answer different questions. Treat each result as evidence, not a guarantee.

Plan an inbox-placement testChoose representative senders, messages and providers, then interpret the limits. Use free checks before paying for a toolCheck authentication, reputation and provider signals without confusing a score with inbox placement. Read the headers from a delivered or spam-folder messageFind the route, authentication results and provider handling recorded in the message.

A blocklist or reputation warning appeared

Confirm which domain or IP is listed, whether the affected provider uses that list and whether real delivery changed.

Put an email blocklist warning in contextCheck the affected asset, provider relevance, underlying cause and recovery evidence. Record the incident and recent changesBuild a dated picture of the symptom, affected route, tests and outcome.

A message bounced or the provider returned an SMTP error

Keep the complete response code, provider name, time and sending route. Those details are more useful than the label hard or soft bounce alone.

Read bounce and SMTP errorsSeparate permanent rejection, temporary deferral, policy failure and authentication failure. Interpret Gmail 550 5.7.26Use the exact rejection text to identify missing authentication or alignment. Collect route and authentication evidenceUse headers when a message arrives somewhere unexpected or a test recipient can provide the original.

An unknown sender appeared in a DMARC report

It may be a forgotten legitimate service, forwarding, misconfiguration or unauthorised use. Identify ownership before authorising or blocking it.

Small business email authentication checklist you can actually verifyCheck domain ownership, sender routes, SPF, DKIM, DMARC, privacy, recovery and monitoring with evidence another administrator can confirm. Build a sender inventoryConnect every sending service with a business owner, domain, DNS owner and review date. Trace website and application emailFind the hosting service, SMTP relay and domain used by forms and automated messages. Read the source in a DMARC reportUse volume, authentication and alignment evidence to decide what to investigate. Review several domains and subdomainsKeep ownership and sending routes separate across brands, clients or business units.

More practical guides

Open the guide that matches the question or fault you are dealing with now.

Why forwarding and mailing lists can break email authenticationTrace how forwarding and mailing lists change the route or signed content, then read SPF, DKIM, DMARC and ARC without weakening DNS to fix one indirect path.How to fix a broken SPF record: duplicates, oversized policies and stale sendersFix a duplicate, broken or oversized SPF record without guesswork. Diagnose the failing route and correct the record safely.DKIM selector troubleshooting: fix failed signatures without guessingA DKIM failure is rarely just a bad DNS record. Read the selector from a real message, query the exact key and separate DNS faults from signing changes.