Julian Kippels writes:

If someone joins a mailinglist there is a process where they have to opt in by replying to a welcome mail. I would like to know for how long this opt-in is valid? Or does it never expire?

I suppose you mean how long the token is valid before it can't be used to confirm the address? By default, 3 days. This value is recommended as giving the user plenty of time to confirm without cluttering the database.

It can be changed in mailman.cfg in section [mailman], key 'pending_request_life'. See schema.cfg for the file format. (Settings in mailman.cfg override those in schema.cfg.) The format of the value doesn't seem to be documented, but it accepts the units you'd probably expect for this kind of thing: s = seconds, m = minutes, h = hours, d = days, w = weeks, and "reasonable" combinations such as "2h30m" (not sure about the exact rules but I think it's basically the unit comes after the number, and you can't repeat units).

Steve