Guides
Guides for people who run mail
What we have learned running a relay since 2007, written down for mail admins and developers. Standards and provider documentation cited, our own observations marked as such.
Rotating a DKIM key without a minute of unsigned mail
DKIM keys are rotated by publishing a second key next to the first and moving the signing over, not by replacing anything. Here is the order of the steps, how long to wait between them, and what happens when a step is skipped.
Read the guide →SMTP relay or email API: which one, and when both.
Both reach the same relay, the same IP addresses and the same delivery log. The choice is about what is sending the mail, not about which sounds more modern.
Read the guide →