We have noticed one particular IMAP account using 17gb of bandwidth yesterday and 12gb today.

The account holder sends and receives few emails.

The logs show connection to his cell phone and desktop every 5 minutes and disconnect a few seconds later which is normal. No email is being sent and only a few received today, some with small attachments of a few mb.

The rate of bandwidth increase  seems to be about 1gb per hour. He has a small number of emails on his account - it's not like he is synching 1000's of emails. I'd say his usage is in the lower 5% of our customers' usage.

This appears to have happened since we upgraded although that could be a red herring. As I have only noticed it on a single account it would suggest an issue with that account and even a false value in the stats?

Has anyone else experienced this? What could cause it? Is there anyway I can get to a higher granularity in investigating what is increasing the bandwidth at this rate
 

*Our bandwidth on IMAP was typically 5gb per weekday. yesterday after upgrade was 58gb and today 20gb thus far. Coincidence?