[Users] How does the "master passphrase" config option work?

[Phil]

Hi everyone, 1st message here, I really like Claws mail, it's a
refreshing change from TBird, thank you *very much* to everyone making
it, it works really good for me.

I'm wondering how the "master passphrase" config option works : I
checked it in the preferences dialog under other/miscellaneous some
days ago, but nothing changed : Claws still asks for each password, two
(IMAP / SMTP) for each account, which can be quite time-consuming,
especially when in a hurry to send or receive something.

I tried unchecking "save for this session" in the password entry
dialog, but this option just behaves as advertised... I must be missing
something, maybe an encryption lib?

--
Phil