1,657 votes/dev/rob0 commented
Without reading the whole comments here (just the first page, sorry), there really is no way to do this. The Postfix MTA allows multiple, configurable delimiters. And you can never be sure that a delimiter character IS a delimiter. I can create an address like this: <"Eat @ Joe's One-Stop + Get Gas"@example.com>, and it would be perfectly valid. The localpart can contain ANY printable 7-bit ASCII characters from decimal 32 to 127 inclusive; the limit is max 63 characters. Don't take my word for it, see RFC 5322.