Confirmation e-mail for my account is not sent

I’m trying to set for my gitlab account, but I don’t get the confirmation e-mail for that address. I’ve tried to resend it several times. Spam folder is empty. My mail provider even checked the logs, but the mail never arrived.
When I change the local part to something else (e.g. the confirmation e-mail arrives instantly. I’ve had that experience also with a couple of other services on the internet when I used the service name in the local part of the address, but I never found out the reason for that.

ps: is only a placeholder for the real domain

I wonder if it is the same as what I posted here and raised as a bug in Gitlab CE Issue #65501. I don’t think it is a configuration problem.