Look up the instructions for your mail provider to set up SPF, DKIM, and DMARC records in your DNS so email services know which emails sent from your domain are actually legit. Without those records telling email servers what’s valid and how to handle what’s not, it’s basically the Spiderman pointing at Spiderman meme.
Somewhat related, I’m so annoyed that my USB 3.0 SATA adapter doesn’t pass S.M.A.R.T. data. Didn’t even think to check for such a deficiency. Just another thing to watch out for when buying these adapters.