Yuka on Nostr: I still fail to set these things up. ...

I still fail to set these things up.

quoting
note1csx…tg6y

If you provide email services to your customers, you can save yourself a lot of grief by ensuring SPF, DMARC & DKIM are configured on their accounts.

Bouncebacks are your friend, and they really aren't difficult to read.
Error 4.5.1

Google, Hotmail, and many others now require all three to be enabled for email sender authentication.