Allow emails with "+" in email catchall address

short description

I triend to create a catchall email for a domain and send it to myemail+server1@exaple.com. I got the error Destination is no valid email address.. I searched the code and found that in https://git.ispconfig.org/ispconfig/ispconfig3/blob/master/interface/lib/classes/tform_base.inc.php#L1044 there is a validation check to not allow "+" signs in the email. I suppose it is for the moment when you create a mailbox on the server.

Allow "+" sign in emails that are as recipients, in Email Catchall, Email forwarding and others.

Add a parrameter that will allow skipping of the check. We have a separator parameter so I think it's possible to add another one.