After you go through and set up the 'all access' rights in your keychain, be sure to edit your keychain settings (Edit -> Change Settings for Keychain "whatever"), and make sure Lock after x minutes of inactivity isn't checked.
If it is checked, you can do everything else right, but keychain will keep getting locked every few minutes, prompting keychain password requests when checking email.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20071020085126389