Solved: Emails with a plus sign don't work for verification

[RealSnoopyDog]

Hi, today I tried to change my mail address. The new address looks like this:

xxx+yyy@domain.tld

The "+" is an allowed character in the local part of the mail address since the very beginning (1982 I think). In other forums I have no problems but here I never receive the confirmation mail when I use an address like this

[RealSnoopyDog]

I found the problem: the spam settings of my mail account seem to reject mails from server which are on several black lists. If I disable this real time blacklist check, then I receive also mails with a "+" in the mail address.