A closer look at the email shows @RokeJulianLockhart is using addy.io the “Anonymous Email Forwarding service” so most likely it will happen again, based on experience with other users who ended up using a non anonymous email address.
@Nick-Hall and @gramps-project, thanks. However, it’s merely a sieve, which allows me to automatically label based upon recipient, rather than sender (my subdomain is my real name). Do you happen to know what e-mail address the rejected mail was sent from? I’ll ask the developer to whitelist it:
If, instead, the reason that it was rejected was due to a large attachment, etcetera, I’ve also asked mantisbt.org/forums/viewtopic.php?t=40347 in the meantime. If so, I’d like to know what caused it.