Several of my users are being locked out of their accounts multiple times a day, and I am trying to track down the cause. I have been watching the logs for a pattern, and there are a number of entires that I can't quite make sense of. I'm new to Zimbra, so I'd appreciate some help.

In one series of audit.log entries, it looks like an alias account is trying to log into a user mailbox and failing:

/opt/zimbra/log/audit.log.2011-02-20:1186:2011-02-20 23:01:09,529 WARN [btpool0-16136://] [name=usermailbox@ourserver;ip=192.168.XXX.XX;] security - cmd=Auth;; protocol=soap; error=authentication failed for alias, invalid password;

If anyone has any thoughts, I would greatly appreciate them. I don't want to have to turn off account lockout, so I'm looking for other options.