//The maximum total length of a domain name or number is 255.

The maximum total length of a user name or other local-part is 64 however, here we double it, since a few major services don't respect that and go over.

The maximum total length of a reverse-path or forward-path is 256.

The minimum total number of recipients that must be buffered is 100.

Parse Email Addresses according to https://tools.ietf.org/html/rfc5321.

Parse productions according to ABNF in RFC5322.