If your Mail program or Server connection is constantly asking you to re-enter your password, even when you've asked it to remember your password, you may have a corrupt Keychain entry. To fix this issue, delete the entry:
1- Quit the affected application or disconnect from the File Server.
2- Launch the Keychain Access application located here:
/Macintosh HD/Applications/Utilities/
3- Search for the entry in question:
- for an email password problem, sort the list by Kind, and scroll
down to the "Internet Passwords" and delete ONLY the entries
associated with the email account that's giving you trouble.
- for server problems, sort by Kind and find the "Network Password"
that is giving you trouble and delete it
- for any other application or service, browse for the affected password entry
or use the search bar at the top, then delete that entry.
4- Quit the Keychain Access application and then try again. You should be prompted again for your password. BE SURE to click the checkbox on the password request window to Remember the password. This will recreate the keychain entry.