Sharing here a list of websites/tools I usually use to check, test or even generate something in case I forgot how does it go:
https://toolbox.googleapps.com/apps/dig/
https://ssl-tools.net/
https://ssl-tools.net/mailservers
https://ssl-tools.net/mails
https://www.checktls.com/TestReceiver
https://www.mail-tester.com/
https://en.internet.nl/test-mail/
https://intodns.com/
https://powerdmarc.com/power-dmarc-toolbox/
https://www.immuniweb.com/ssl/
Hope they will help you too 