Email aliases are not limited to gmail - most MTAs (Postfix, sendmail, etc) have allowed '+' aliases for years now.
I think it's bad advice to just simply filter those out - your customers may be using them to filter emails, track the usage of their email address, etc. Restricting what you think is a valid email address, rather than what I type in, is a pretty assholish move.
On top of all that, it simply won't stop spammers.
I think it's bad advice to just simply filter those out - your customers may be using them to filter emails, track the usage of their email address, etc. Restricting what you think is a valid email address, rather than what I type in, is a pretty assholish move.
On top of all that, it simply won't stop spammers.