Build the records that stop mail being sent as you DMARC
SPF, DKIM and DMARC decide whether the world trusts mail claiming to be from you. They are hand-written records where one slip lets a spoofer through. This builds them right and checks the ones you have.
Your domain
SPF: who may send your mail
DMARC: what to do with mail that fails
DKIM: sign your mail
security.txt: how to report a problem to you
Check a record you already publish
Paste an SPF, DMARC or security.txt record and it is read back for the faults that matter.
Doing this often? The OBSCURA Sovereign Suite keeps checks like this as evidence against the controls of ISO 27001, SOC 2 and Cyber Essentials. On its own, US$4 a month; with everything else, US$9 a month or US$79 a year. 7 days free.