I can't get any mail account to work, every single time I start mail and have to enter a password for the email accounts (all 12 of them) I get this error when I click save, therefore No Email Works 😠:
Unable to store credential due to error -25308 Requested By: Mail
I had the same problem (fastmail), but now it has gone away. What I mean by that is that I fiddled around with it for a while, shutdown Mail.app, and an hour later, after reading your message, fired it up again to see if our messages matched and boom. It works.
Open Keychain Access and remove any stored passwords for those accounts. Or just delete the keychain and reboot, letting it create a new one. I've seen a few other threads where Microsoft applications kept giving credential errors and required the deletion of the matching entries in the keychain.
I also ran into this error; I managed to get this to work by opening Keychain Access, selecting one of my mail accounts' password entry, revealing the password (requiring entering my login credentials), and then restarting Mail.app.
I upgraded a working system to Sierra, and immediately after the upgrade my existing email accounts were broken. I shut down, rebooted, and everything was OK. (Well, at least the accounts worked - there were numerous other bugs.)
I've noticed this in many previous OS upgrades: at the conclusion of the upgrade process, you are left logged in with a broken system. Shutdown/reboot is necessary to get the system working properly.
Looks like a restart fixed it for me...
Same problem for me, cannot get any of my IMAP accounts to work anymore.
One account was working originally, but after deleting the keychain trying to get the other ones up and running, now every account is broken.
Rebooting does not solve anything for me either.
Did you sign into your icloud account and sync the keychain? That is causing the problem for me and the mail program would open but only for a few minutes and it would shut down. Just deleting the Keychain entries was not enough, iCloud would just add them back. I had to uncheck the Keychain in the iCloud prefs and added the mail account manually and everything is now working great!! I must have some corrupted entries in the keychain or the settings have changed from El Capitan and Mail doesn't like them.
I have no isses with this. It just went through some configuration setting at start up and works fine.
