To clarify the SMTP RFC (RFC 5321) says that a valid e-mail address is defined in RFC 5322 - Internet Message Format. RFC 5322 does say that a `+` is a valid c

To clarify the SMTP RFC (RFC 5321) says that a valid e-mail address is defined in RFC 5322 - Internet Message Format. RFC 5322 does say that a `+` is a valid character in the local part of an e-mail address. The `+` character being used for address aliasing is, as far as I can tell, not mentioned in RFC 5321 or RFC 5322