Identical Addresses treated differently causes redundancy in address list

In accordance with RFC standards, certain special characters such as 'plus' (+) symbol are allowed to be used in 'local part' of email addresses. Thus the addresses <email address hidden> and <email address hidden> are considered to be valid.

Also, certain mail service providers such as gmail accepts as using the '+' symbol in an address and appending any number of characters after the 'plus' giving an option to filter the emails utilising the '+' for filtering and all those set of email addresses with different sets of characters after '+' yet address to a single account.

On the other hand, Mailman doesn't processes 'plus' in any special way than a normal character and as a result two or more email addresses can be subscribed pointing to the same account for the same mailing list...This can cause redundancy of addresses in subscriber database and also multiple emails might go to the same user and thus even the important mails may be treated as spams.