If you have an iPhone or iPad with IOS 6.1 AND your email is hosted Exchange, you may experience some issues.
Below is a message from Appriver re: an issue with Apple devices connecting through hosted Exchange. The gist of the article is that there is not an immediate fix, but both Apple and Microsoft are working on a solution. In the meantime, if you are affected, they have a workaround, which we can help implement if needed. Conspiracy theories anyone?
“ Apple iOS 6.1.x connection problems
Apple mobile device users (iPhone/iPad/iPod) who have upgraded to iOS 6.1 or 6.1.1 may experience connection issues with Hosted Exchange mailboxes. If you have not upgraded to iOS 6.1 or 6.1.1, please do not do so yet . If you are experiencing connection issues with your upgraded iOS, the only fix available now is to remove your Exchange mailbox connection, wait 30 minutes and then add your Exchange connection without your calendar. That would mean your iOS device would not sync with your mailbox calendar.
Apple and Microsoft are both actively working on this issue and if anything changes we will update our notice.”