- email-security-scans.org
- Port25’s Authentication and Spam Assassin Tool
- verifier.port25.com - send an email to this address to check headers
- multirbl.valli.org - "The complete IP check for sending Mailservers"
- postmastery - Check the DNA of your email against important best practices using our free email deliverability test.
- email-security-scans - Public Email & DNS Testbed - Considering just DKIM tests, this one is the only tester which explicitly and clearly recognizes ed25519 signatures. For the rest, EmailAudit reported a pass, but then said "DKIM key size is 0 bits. More senders are starting to use 2048 bits."
- internet.nl - test website, email, connectivity
- Wander Science DKIM Test
- uriports - Test and optimize SPF, DMARC, DKIM, and MTA-STS
- Google Admin ToolBox - Check MX - maybe be broken in some aspects, take with grain of salt
- Easy DMARC - verify dns data
- dmarcian - DMARC resources
Note: seems ';' (semi-colon) in records may help with some records.
- send an e-mail to spf@tester.realsender.com
- check online the validation results (it will take a minute to appear) realsender