I think I have a similar problem as mentioned in this thread (although my german sucks).
"error_email_wrong" is thrown when trying to register or trying to write to me in the standard form:
https://www.jernbanen.dk/forum/index.php

There were 2 "error_email_wrong" entries in the lang-file but deleting one of them didn´t change anything.

I have tested with a variety of email addresses like .dk .se .com and in different browsers.

Some users are able to register though - latest user registration was on 31. October.

PHP-version: 7.4
MLF-version: 2.4.13

What to do?

/Tommy