Does the local part of an e-mail address have a minimum length requirement?
It is entirely possible to have an e-mail address with just one character. All of the guidelines are defined in RFC822: http://www.ietf.org/rfc/rfc0822.txt?number=822
The necessary REGEX: http://www.ex-parrot.com/pdw/Mail-RFC822-Address.html
0, if you don’t count quoting double-quotes. If you do, the minimum’s 1.
""@example.com
RFC 5321
Mailbox = Local-part "@" ( Domain / address-literal )
Local-part = Dot-string / Quoted-string
; MAY be case-sensitive
Dot-string = Atom *("." Atom)
Atom = 1*atext
Quoted-string = DQUOTE *QcontentSMTP DQUOTE