You’ve been locked out!
For some strange reason, my network account would be locked by the domain controllers on the network and I couldn’t authenticate using my credentials.
My workstation authenticates either through an ActiveDirectory server or an OpenLDAP server and only recently, I’ve been having problems with Apple Mail asking me for my password over and over again or my workstation not being able to log into the network.
I looked at the Console app to see if I could get more information and with some help from my IT admin, we were able to find the cause of the problem: the Contacts program was unable to bind to the authentication server.
So, I popped into Contacts, opened the app preferences and… would you look at that! The password I had changed for my account was not updated in Contacts.
That seemed a little silly that the System Preferences was able to change my LDAP password, but the Contacts app would hold it’s own copy of my network password.
When Apple Mail would query the Contacts program, the application would attempt to log in several times on the ActiveDirectory server, using the wrong credentials, and cause my account to be locked out.