Registration emails sometimes not sending

I just got my WP site up and I have a strange little problem with user registration.
I tested it with myself, using my personal email as the new user, while my admin account is under “myname”@Mydomain.com sort of thing (which eventually forwards into my personal email anyway). I get the Reg screen, enter a UN and email, and itsays that an email with PW has been sent. Then, to my admin email, I get the “New user has joined” email all okay, and on my Users screen it now lists the new user, but my user account has never been sent an email with the PW. Nor does triggering a resend (Forgot PW) do anything.
But making it even more strange is that when I had someone else register as a test, they received their new user email complete with PW nearly immediately (and sent me a copy of the text of said email, which confirmed for me that it was correct).
I’ve turned my spam filter on earthlink completely off, and still nthing. I checked every setting I could, I installed “SB Welcome Email Editor” so I could alter the From Addy and such in case that was a problem, and still the same problem. Does WP not like sending to earthlink, maybe? Or just not like my address? I changed up using different user names with the same email (deleting old test users first before trying again)., and still the same.
Help?

site is https://www.maldene.com