The bulk sender rules, summarised
9 July 2026 · 5 min read
The major mailbox providers now enforce a baseline for anyone sending at volume. Most of it was already best practice; the difference is that it is now checked.
The requirements
- SPF and DKIM, both, with DMARC published.
- Alignment with the visible From: domain.
- One-click unsubscribe on bulk mail, honoured within two days.
- Spam complaint rate kept low, well under a percent.
- Valid forward and reverse DNS for the sending IP.
Which parts bite
The complaint rate. Authentication is a one-off configuration job; complaint rate is a permanent consequence of who you mail and how often. If you are over, no amount of DNS will save you.
More on deliverability
SPF, DKIM and DMARC in plain English
Three records, three different jobs, and one relationship between them that explains almost every "why is my mail in spam" question.
Why forwarded mail lands in spam
Forwarding breaks SPF every single time, by design. What keeps forwarded mail out of the spam folder is DKIM surviving the trip, and that is easy to break.
MTA-STS and TLS-RPT, and when they are worth it
SMTP encryption is opportunistic by default, which means it is trivially downgraded. These two records are the fix, and one of them is nearly free.