5 ms·
POP3 – UIDL is a required command
- theamk 6y agoI disagree with the author when they dismiss Message-ID as unreliable. I believe that rather than trying to get everyone to fix POP3, the right way is to download the message again on failure, and de-duplicated based on Message ID. In practice, it is pretty reliable -- even when it is not set by the sender, most MTAs will add it if missing. So your origin "sendmail" will generate one, and failing that, the smart host will, and failing that, recipient's MTA will. And the common format often includes GUID or high-precision timestamp, so the collisions are pretty unlikely.
- billpg 6y agoBuy me a drink and I'll tell you about the time I investigated a service that, among other things, sent email with a Message-ID based on the date. (Not the time of day.) It was meant to send one email every day. Until it wasn't.
- theamk 6y agoThis just looks like a broken sender - I mean, RFC5322 is pretty clear that "The generator of the message identifier MUST guarantee that the msg-id is unique." I know that practically, we want to support every email out there, even if it is not quote RFC compliant -- but how far do we want to go? Is it worth adding all new mechanism just because someone out there may be sending non-compliant messages? Especially given that those non-compliant messages are likely to break other things like mail databases, IMAP UIDVALIDITY and so on?