I didn't explain myself very well. I was running out the door as I wrote my original message. Not a good idea.
I'm running MediaWiki v1.34.2 on Linux Mint v20.1.
For your info, 1.34.2 is an unsupported, outdated, insecure version. You may want to upgrade for your own safety and the safety of all your users: https://www.mediawiki.org/wiki/Manual:Upgrading
Three or four days ago I began getting emails like below. (ImmigrantJohnLakeOfGravesend is my MediaWiki page.) I've received maybe 40-50 such messages. The error type is sometimes different. And occasionally a message seems to be delivered because I receive a "real looking" response.
Can someone tell me what's going on, and what I can do about it?
Someone registered an account on your MediaWiki installation and they entered an email address when registering that account. The mailbox of that email address is full, hence the mail server of that MediaWiki installation cannot deliver the message, so it reports "550 Mailbox is full". The mail server does not give up after one attempt to deliver the message so it regularly tries (and fails) again.
(I don't know what "real looking" is supposed to mean.)
By "real looking" I mean the outgoing activation confirmation message actually got delivered and I received a real (albeit seemingly automated) response rather than an error email.
My MediaWiki page (ImmigrantJohnLakeOfGravesend) has a small finite audience. On the same day (seemingly) my page received 532 new registration requests, all from email addresses I do not recognize (I would most likely recognize an email address in my small, finite community).
To me, this seems like spam or an attack of some sort. What can I do about it? Will upgrading to 1.35.x resolve this issue?