Other than for POP3 accounts Claws Mail forgets the password for an IMAP4 mailbox after half an hour OR going off- and online again OR suspending to RAM. Reproduction: 1) You have an IMAP4 and a POP3 account with no passwords saved 2) Fetch mail manually and enter the two passwords 3a) Press Ctrl-w to work offline, and Ctrl-w to go online again 3b) OR wait for 30 minutes 3c) OR suspend to RAM and resume your PC 4) Fetch mail manually for the second time -> You have to enter the password for the IMAP4 account again! (But not for the POP3 one) Tested on Ubuntu 8.10 and 9.04 with Claws Mail 3.5.0 and 3.6.1. The option "Remember password for this session" (new with 3.5.0cvs105?) does not change this behavior. If "Automatic checking for new mail every" 25 "minutes" is enabled Claws Mail does not ask for a password again when fetching manually. Unfortunately this can not be set individually for every account. The behavior is the same with and without TLS/SSL.
I think it's been fixed in 3.7.1. (At least it works for me...)
Absolutely not fixed! version 3.14.1, Debian 9.1, Xfce DE. Claws still forgets IMAP passwords. It must be included in Claws, not in some OS password manager.