once in a while i’m involed in moving mail servers around, to and from the could. those tools are useful each time it’s done:
- https://www.mail-tester.com/ + https://app.mailgenius.com/ – check how e-mails sent by you are seen by spamassassin and other mail filters
- https://dmarcian.com/domain-checker/ – check of DKIM, DMARC, SPF records
also related – a deep dive into e-mail delivery in 2024.