Exchange email
We are experiencing an issue where exchange email on user iPhone's keep re downloading the mailbox messages. This is happening on two separate domains with two different exchange 2010 servers. This issue happened in the past and was resolved by iOS 9.3.1. The issue re-occurred again last Thursday (5/12/16). Removing the mailbox, performing hard reset, re-adding the mailbox didn't correct the issue. Wiping the phone and recreating the mailbox from scratch also didn't correct the issue. When the email re-downloads on the iPhone it will work for about 40 minutes - 1 hour before it starts re-downloading all the messages again. I have had to use Microsoft Outlook app for iOS as an alternative while we try to figure out this issue. Can anyone make any suggestions? I noticed iOS 9.3.2 came out today but it doesn't mention fixing the issue I have been experiencing. This issue mostly occurs on older iPhone's such as iPhone 5 and iPhone 5S's but we also had a few users with iPhone 6/6S with the same issue.
iPhone 6s, iOS 9.3.1