Blogs
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Deliverability
Why Gmail Shows a Phishing Warning on Your Email Even When SPF, DKIM, and DMARC All Pass
Authentication passing is not a clearance signal. The documented Gmail enforcement for a high user-reported spam rate produces no bounce and no DMARC report, so the fix starts where the logs stop.
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Deliverability
Why Corporate Mail Servers Soft-Bounce Your Email and How to Read the Bounce Code
Corporate recipients soft bounce far more than Gmail or Yahoo, because their gateways are stricter and their mailboxes disappear. The three-number status code tells you which problem you actually have.
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DMARC
Should You Keep Collecting DMARC Aggregate Reports After You Reach p=reject?
Most domains at p=reject stop asking for aggregate reports. Here is why that is a mistake and what those reports still show you after enforcement.
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DMARC
What to do when a free DMARC monitoring tool restricts the domain you can monitor
Free DMARC monitors tighten their domain verification rules after acquisitions. Here is how to keep your aggregate reports, re-route them, and pick a tool that won’t lock you out.
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Deliverability
What the Measurement Data Shows About MTA-STS, DANE, and BIMI Adoption
After DMARC enforcement, three other email security protocols come up. MTA-STS adoption sits in the single-digit percent range for top million domains. DANE stays tiny because it requires DNSSEC. BIMI is uneven across mailbox providers. Here is the realistic adoption picture and the order to deploy.
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SPF
How to configure SPF for a custom domain used with Brevo (Sendinblue)
A working Brevo SPF record is one include statement on your sending subdomain. Here is the exact directive, where to put it, how to combine it with other ESPs, and how to verify it before you send a campaign.
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Deliverability
Why Yahoo and AOL Started Rejecting Your Mail with 550 5.7.9 in October 2026
A new enforcement wave at Yahoo and AOL started returning 550 5.7.9 policy rejections and 421 deferrals for legitimate senders around 2026-10-06. Here is what is causing it and how to diagnose and fix it.
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DMARC
How to Stop Backscatter NDRs When You Enforce DMARC
Backscatter NDRs flood your inbox the day you flip DMARC to p=reject. Here is why and three concrete ways to stop them.
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DMARC
Why You're Suddenly Seeing More Incoming DMARC Failures (and What To Do as the Receiver)
The rising tide of incoming DMARC failures across senders in 2026 is real. Here is the receiving-side explanation and a triage workflow for sysadmins.
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DMARC
Why Email Receivers Disagree on Your Authentication Even When SPF, DKIM, and DMARC All Look Correct
When authentication looks clean in DNS but receivers reach different verdicts on the same message, the answer is rarely alignment. It is that each receiver is testing different layers, combining them differently with reputation, and surfacing different things in RUA reports.