Blogs
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Deliverability
Why Exchange Online Moderation Accepts Your Email But Then Rejects It with 550 5.7.134
Exchange Online moderated connectors accept external messages for approval, but then reject them with a 550 5.7.134 error during delivery. Here is what causes it and how to fix it.
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DMARC
How to Move Your DMARC Policy from p=none to p=reject Without Breaking Email
Moving DMARC from p=none to p=reject breaks legitimate mail when third-party senders are not properly configured. Here is the step-by-step process to enforce DMARC safely.
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What to Do When DMARC Reject Policy Generates Failure Reports You Cannot Interpret
DMARC p=reject often triggers failure reports from legitimate senders. Learn how to read these reports, diagnose the root cause, and fix common alignment issues without weakening your policy.
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DMARC
How to Stop DMARC Backscatter When Attackers Spoof Your Domain
Your DMARC p=reject policy is working but you are drowning in bounce notifications for mail you never sent. Here is why backscatter happens and how to stop it.
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DMARC
Your DMARC Report Shows Failures But Email Is Still Going Through - What That Actually Means
DMARC aggregate reports show thousands of failures yet email delivers normally. Here is what those numbers mean, which failures to investigate, and what to do first.
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Deliverability
How to Stop Marketing Emails From Blocking Your Transactional Auth Emails
When marketing campaigns and transactional auth emails share the same sending infrastructure, high-volume marketing sends can delay login links, password resets, and 2FA codes. Here is how to diagnose and fix it.
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Deliverability
How to Stop Marketing Emails From Blocking Your Transactional Auth Emails
Login emails blocked or delayed during marketing campaigns? Shared sending infrastructure is almost always the cause. Here is how to fix it fast.
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Deliverability
Why Your Emails Fail Gmail Because of PTR Records
Your SPF and DKIM pass but Gmail still rejects your custom domain emails. The cause is often a missing or mismatched PTR record. Here is what PTR records are, how to check yours, and how to fix Gmail deliverability issues caused by reverse DNS.
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DKIM
DKIM2 and DMARCbis — What Email Operators Need to Know
DKIM2 upgrades cryptographic key sizes and adds ECDSA support. DMARCbis updates the DMARC standard with new policy tags. Here is what changed, what it means for your email setup, and how to test safely.
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DMARC
Why Your Subdomains Need Their Own SPF and DKIM Records Even When They Inherit Your DMARC Policy
Your root domain DMARC policy applies to subdomains automatically, but SPF and DKIM do not follow the same inheritance rules. If your root domain uses p=reject, a subdomain without its own aligned SPF and DKIM will silently fail DMARC.