Download the UW c-client and check the file c-client\imap4r1.c
.
The great majority of the error messages are reproductions of the error messages the IMAP server has sent. I found a few that were predetermined, though. Here they are:
mm_log ("Scan not valid on this IMAP server",ERROR);
mm_log ("Unable to negotiate TLS with this server",ERROR);
mm_log ("IMAP Authentication cancelled",ERROR);
mm_log ("Can't do secure authentication with this server",ERROR);
mm_log ("Server disables LOGIN, no recognized SASL authenticator",ERROR);
mm_log ("Can't do /authuser with this server",ERROR);
mm_log ("Too many login failures",ERROR);
mm_log ("Login aborted",ERROR);
mm_log ("[NOTUIDPLUS] Can't do UID EXPUNGE with this server",ERROR);
mm_log ("Excessively complex sequence",ERROR);
mm_log ("Can't access server for append",ERROR);
mm_log ("ACL not available on this IMAP server",ERROR);
mm_log ("Quota not available on this IMAP server",ERROR);