Passwords and file sizees

Hello
This is my first post here.
I installed Thunderbird Portable without any trouble.
When I setup the accounts I noticed that there was no field for the account pasword like in Outlook Express.
When I tried to check for emails, of course there was a popup requesting the password. This popup ocurs every time Thunderbird is launched. I noticed that there is a check box for using a 'Password controler' (or something similar in name). Once I checked this box my password is now remebered.

My question is, where is this password controlling application?

My other question is, what is the maximum file size in the Mail subfolder?
Thanks