I am trying to configure Xeams to pull user authentication from AD/LDAP. I have successfully configured this and am able to authenticate to the web interface as AD users; I am able to authenticate to SMTP as those users, but if I try to authenticate via IMAP I get the following in the logs:

I am able to authenticate as a local Xeams user to IMAP - am I missing somethign in the username format?

2020-05-02 18:35:28,837 - - [ 58] ************** New Connection from: 40.90.221.225 **************
2020-05-02 18:35:28,837 - - [ 58] S <-- * OK Synametrics IMAP4rev1 server ready 5/2/20 6:35 PM
2020-05-02 18:35:29,096 - - [ 58] C --> BT1 LOGIN "user@domain.com" xxxxxx
2020-05-02 18:35:29,096 - - [ 58] S <-- BT1 BAD Excepted parameters not found
2020-05-02 18:35:29,233 - - [ 58] C --> BT2 LOGOUT
2020-05-02 18:35:29,233 - - [ 58] S <-- * BYE IMAP4rev1 IDLE Server logging out
2020-05-02 18:35:29,233 - - [ 58] S <-- BT2 OK LOGOUT completed
2020-05-02 18:35:29,233 - - [ 58] ~~~~~~~~~~~~~~ Connection closed: 40.90.221.225 (396 ms)~~~~~~~~~~~~~~
2020-05-02 18:35:40,113 - - [ 59] ************** New Connection from: 40.90.221.225 **************
2020-05-02 18:35:40,113 - - [ 59] S <-- * OK Synametrics IMAP4rev1 server ready 5/2/20 6:35 PM
2020-05-02 18:35:40,366 - - [ 59] C --> BT1 LOGIN "user@ad.domain.com" xxxxxx
2020-05-02 18:35:40,366 - - [ 59] S <-- BT1 BAD Excepted parameters not found
2020-05-02 18:35:40,502 - - [ 59] C --> BT2 LOGOUT
2020-05-02 18:35:40,502 - - [ 59] S <-- * BYE IMAP4rev1 IDLE Server logging out
2020-05-02 18:35:40,502 - - [ 59] S <-- BT2 OK LOGOUT completed
2020-05-02 18:35:40,503 - - [ 59] ~~~~~~~~~~~~~~ Connection closed: 40.90.221.225 (390 ms)~~~~~~~~~~~~~~
2020-05-02 18:35:49,646 - - [ 60] ************** New Connection from: 40.90.221.225 **************
2020-05-02 18:35:49,646 - - [ 60] S <-- * OK Synametrics IMAP4rev1 server ready 5/2/20 6:35 PM
2020-05-02 18:35:49,884 - - [ 60] C --> BT1 LOGIN "user" xxxxxx
2020-05-02 18:35:49,884 - - [ 60] S <-- BT1 BAD Excepted parameters not found
2020-05-02 18:35:50,013 - - [ 60] C --> BT2 LOGOUT
2020-05-02 18:35:50,013 - - [ 60] S <-- * BYE IMAP4rev1 IDLE Server logging out
2020-05-02 18:35:50,013 - - [ 60] S <-- BT2 OK LOGOUT completed
2020-05-02 18:35:50,014 - - [ 60] ~~~~~~~~~~~~~~ Connection closed: 40.90.221.225 (368 ms)~~~~~~~~~~~~~~