Before MAPI many of our customers were using EAS with Outlook to get as close to Exchange functionality as possible. Somewhere along the line we were told that EAS was only for mobile devices. Anyway… about 5 out of maybe 20 EAS clients got hosed after the upgrade. Their Outlook inbox showed empty yet shows “all folders up to date” so they were very scared that they lost everything until I assured them that all data was on the server. I tried a few different solutions to try and fix it but in the end all those accounts had to remove the account in Outlook, add it back, and let the account resync. For a few users it was no big deal but a few had 10-20gb of data and they weren’t happy about it at all.
As best as I am aware it was only the Outlook people that had problems. My PC is on the same LAN as the mail server so it did resync my data without intervention (I watched the inbox go from 9,000 emails down to zero and then started repopulating) and I didn’t have to remove the account, etc.
Eventually I’ll have to migrate all those users PCs from EAS to MAPI. One client is leaving us for O365 so I don’t have to worry about them.
It was a headache but if there were security patches in the update I consider it all good. I’m only now deploying the first MAPI accounts as I waited a number of SM revisions before wanting to roll it out live.