= Email Addresses = Valid '''email addresses''' are effectively an evolving standard. <> ---- == Structure == An email address is composed of a '''local part''', an at sign (`@`), and a '''domain part'''. ---- == Local Part == The local part of an email address is fundamentally a name composed of letters, numbers, dashes (`-`), pluses (`+`), single quotes (`'`), and periods (`.`). The first and final characters typically need to be alphanumeric. A non-compliant local part needs to be quoted with double-quotes (`"`). A mail server ''should'', upon receiving mail, either relay it elsewhere unchanged or deliver it locally. This decision ''should'' be made based on the domain part of the mail recipient; the server ''should'' take ownership over it's own (sub)domain and leave all other mail to other servers. But the reality is that a mail server has full control over the deliverability of locally-destined mail, so effectively anything that a mail server supports is an allowed local part. Many mail servers have decided upon non-standard rules for what is valid and what is invalid. Beyond that, many mail servers do not preserve relayed mail; addresses can be case-folded and re-encoded. TODO: copy table of service providers' support for unusual local parts from https://www.youtube.com/watch?v=mrGfahzt-4Q ---- == Domain Part == Anything that is supported by your operating system's name resolution. ---- CategoryRicottone