Aaryan Bhagat writes:
Well in a crux when the user will resubscribe he will see its previous posts. We have an implementation for that already right?
I read Mark's reply, but I'm still not understanding what you are thinking about. It doesn't seem to be the archive (which after all may not even exist for a given list), but "check the archive" is the standard Mailman answer to finding missed posts.
Let me take this opportunity to frame a discussion of the architecture of Mailman 3 in the context of this thread. There are five ways that a user with address "unsubscribed@example.net" might see a post (whether her own or another person's).
via the list to unsubscribed@example.net (while still subscribed and enabled); this will receive posts only while subscribed and enabled.
That is, Mailman does not send "back issues" (except in the corner case that the subscription is a digest subscriber, they'll receive posts that have accumulated in the current digest issue up to the time they subscribe). If the question is "does Mailman send missed posts in the case of an interrupted subscription", the answer is "no". It also doesn't automatically switch a subscription to a user's disabled address if the enabled address is disabled or unsubscribed. (This would be possible with the current design, but I'm not sure whether it would be a bug or a feature!)
By design, Mailman cannot do send missed posts at resubscription time. The core keeps track of subscriptions and accepts posts and forwards them to enabled subscribers and IArchivers *once*, then forgets them (except for logging the event of a received post and its forwards -- but the message itself is forgotten). Handling temporary failures is the responsibility of the MTA, which may retry delivery many times before giving up and returning a "bounce" to Mailman. Mailman itself sends a post to each enabled subscriber only once.
On the other hand, the archiver keeps track of posts, and doesn't know anything about subscribers. It's true that core provides a way to query a list to check if an email address is subscribed for authentication purposes, but there is no way to get information about posts received (or not received) by that address. Neither the core nor the archiver records that information.
I seem to recall that in the days before the web there were MLMs that allowed you to request that the MLM send you an archive of past posts by mail! But Mailman was designed to take advantage of the web, and doesn't implement that. Instead we access old posts via the web. (Some archivers also allow downloading whole mboxes to get a month's worth of posts.)
via the list to another subscribed and enabled address of that user
as a direct addressee (including their "sent" folder, if you insist you could count this as "3b")
on a another subscriber's or addressee's screen or printed out on paper on their desk
in an archive. This is the generic answer to "I didn't see some posts in my mailbox, how do I read them?"
In case #4, an archive, some kind of authentication (such as list subscription) may or may not be required. But it need not be list subscription: it's up to the archive itself to decide policy. And if it is list subscription, neither the core nor the archive records enough information to identify "back issues" that need to be sent.
Electronic mail delivery is the paradigmatic example of a distributed system, and Mailman 3 just squares that. :-)
Steve