I can only guess that something is either preventing a successful completion of the sync, my usual goto for that sort of thing is anti virus software. Basically file contention from the activities of scanning each change and hacking the encrypted connection to scan traffic has far more unintended consequence that most of us suspect. Then there is the possibility the user has set the compact threshold quite low and their folders are constantly compacting which on an IMAP account involved a resync. The default for triggering a compact is in the megabyte range, I think around 20 as a new profile I recently created is set to that. But there is nothing to say it can not be 200mb Likewise you might want to watch the user and see if they are constantly opening and closing the application or click the get mail button while bored on the phone. A check of their setting to get mail might be appropriate as well. I have seen a lot of folk that think setting it to every minute is acceptable. As it is your server, have you enabled push notifications. That will remove the temptation for most of the silly frequency setting and constant manual checks as mail will be pushed out on receipt.