A curated list of resources on Email tools, server, framework, technology...
DMARC, SPF, DKIM, BIMI checker.
Instantly test your domain to verify your DMARC, SPF, DKIM, BIMI configurations
The Merox solution helps you implement DMARC and many other DNS security protocols and standards.
rotation and revocation of DKIM keys.
dkim-rotate is a tool for managing DKIM (email antispam) keys in a manner that avoids unnecessarily making emails nonrepudiable.
Broadly, dkim-rotate intends to weaken the non-deniable authenticity of leaked and archived emails, while still retaining DKIM’s antispam function. For more discussion of the problem, and the chosen solution, see dkim-rotate(7), and Matthew Green’s article Ok Google: please publish your DKIM secret keys.