Email guides
Written from operating our own Postfix, Dovecot and OpenDKIM stack rather than from reselling somebody else's. Every one of these came out of a problem we had to actually solve.
The guides
DMARC fails but SPF and DKIM pass
Both checks are green and mail still bounces. That is alignment — what it means, how to read it in a minute, and the fix.
p=none to p=reject, safely
How long to monitor, when to quarantine, how to ramp with pct=, and the mistake that silently deletes your own invoices.
Why this stopped being optional
The 2024 Gmail and Yahoo sender requirements were widely treated as advisory. That reading expired.
Enforcement ramped through 2024, escalated in November 2025 from temporary 4.7.x rate-limiting
to permanent 5.7.x rejections, and as of May 2026 Google, Yahoo and Microsoft all enforce.
The consequence changed shape as well as severity. Non-compliant bulk mail is no longer filtered into a spam folder someone might check — it is refused at the SMTP layer. It never arrives anywhere. Nobody bounces it back to your marketing team with a question.
Roughly one sender in three is still partially non-compliant on at least one requirement, and the most common single cause is the alignment problem in the first guide above.
What we are writing next
| Guide | The thing that catches people |
|---|---|
| The SPF ten-lookup limit | Adding one more include: tips you over and SPF returns permerror — which means it stops working entirely, not partially. |
| Reading DMARC aggregate reports | They arrive as daily XML nobody opens. What is actually in them and which fields identify a sender. |
| Warming a dedicated IP | Reputation is earned by volume curve. Send your usual volume from a fresh IP and you will be throttled on day one. |
| Transactional vs marketing streams | Why order confirmations should never share a sending domain with a campaign blast. |
Send us one email and we will read the headers
Forward a message from your marketing tool to hello@spell.agency. We will tell you which domain each check authenticated, whether it aligns, and what it is costing you.
Book a call →