When you setup your email account in Mail ...
Don't use Mail.
Next step: making use of it. (??)
Entourage too offers to store account passwords in the keychain. This also happens with passwords for LAN (including Airport) and encrypted disk image (Disk Util) access, as with iTunes' Store account passwords and those for web page access. And all this is triggered by you entering your account password to access your Mac.
The whole thing about keychain use is that it's
transparent: you never actually have to open the utility. All you see of it is the occasional dialog box asking if you want to store a password, and the utility takes care of the rest: safe storage and autofilling the appropriate password box when presented with it later.
