bug or feature?

[Christof Barth]

Hi,

once in a while (every ten days or so) Mozilla 0.9.3 asks for my mail 
passwords. Preferences are set to save the passwords but it seems to 
forget them intermittently. Is this by design (e.g. security reasons) or 
a bug? If it is by design it should be mentioned in the dialog box.

Christof