Increase number of logged in IMAP sessions to 50000

[link2xt]

Maybe we should increase it more, if we hit 1024 already than it will be hit again when there are 20 times more users. And 1024 connections is not that many users, many have multi-device, multiple accounts etc.

[hpk42]

yes, let's maybe go for 40K (but also dovecot has a client-limit of 20K, which needs to get increased i think)

[link2xt]

client_limit is about not logged in users, once they are logged in they don't count. imap process has client limit of 1 as described in the comment.