RFC 5322 does actually specify this, but it is very indirect. Section 1.2.2 says: This specification uses the Augmented Backus-Naur Form (ABNF) [RFC5234] notation for the formal definitions of the syntax of messages. In turn, Section 2.3 of RFC 5234 says: NOTE: ABNF strings are case insensitive and the character set for these strings is … Read more
email.utils has a parsedate() function for the RFC 2822 format, which as far as I know is not deprecated. >>> import email.utils >>> import time >>> import datetime >>> email.utils.parsedate(‘Mon, 16 Nov 2009 13:32:02 +0100’) (2009, 11, 16, 13, 32, 2, 0, 1, -1) >>> time.mktime((2009, 11, 16, 13, 32, 2, 0, 1, -1)) 1258378322.0 … Read more
According to RFC2822 – Internet Message Format, the short answer is that the “Message ID should be unique for each instance of the message“; however, the MESSAGE-ID field is considered optional and how the MESSAGE-ID field is created is up to the server. Quoted below: The “Message-ID:” field provides a unique message identifier that refers … Read more