As far as email is concerned, "+" is just a character as any other. You might as well configure your mail server to ignore everything from the first "g" in the localpart when figuring out which mailbox to deliver to. Some mailservers happen to do this with a "+", if it happens to occur in a localpart, but that is just what they happen to be doing. There is nothing technically wrong with an email address like "[email protected]" or "[email protected]" or "[email protected]", and "[email protected]" is a different address than "[email protected]", unless the operator of example.net explicitly specifies otherwise.