Email address validation rant

This is my canned pre-written gripe to send to website’s who don’t allow all valid email addresses to be entered into their registration forms….

Dear web developer,

Your website does not accept all valid email addresses in one or more forms where you allow a user to enter their email address. Importantly it does not accept the plus sign “+” which *IS* valid and is widely used as a feature called sub-addressing, see below. Furthermore there are many more special characters which are being blocked but that are in fact valid email address characters allowed by the RFC specs, see below.

Sub-addressing: Also known as plus addressing or tagged addressing. Some mail services support a tag appended to the local part, such that the modified address is an alias to the unmodified address. For example, the address denotes the same delivery address as The text of the tag may be used to apply filtering, or to create single-use addresses.[9] Some IETF standards-track documents, such as RFC 5233, refer to this convention as sub-addressing.

Google’s Gmail takes advantage of sub-addressing:

Note that there are many special characters which are valid
RFC 822

Please bring your system up to spec and support all valid email addresses.

Thank you
Mike Makuch