Outlook Anywhere

I have a user when connecting from home outlook2010 anywhere they sporadically from time to time get locked out. Not sure why this is happening only at home it seems. Usually the password box pops up and he types his correct password. Any reason why he would get locked out from outlook anywhere at home?

 

Perhaps this will help: http://technet.microsoft.com/en-us/library/cc179036.aspx

 

yea i reviewed most of these settings already. Not sure why he would get locked out at home on outlook anywhere. He knows his password so not sure of the issue.