I just got this same error using the latest beta build.  The message was received just fine, then when I went to reply to it the conflict icon showed up (and there doesn't appear to be any way to clear it out).  Here's a screenshot:

Ironically - the subject of the message is having to do with the fact that this person hasn't been able to receive email to their phones since we installed our first "production ready" Beta (which I think was the 3rd release).  Both of those users are connecting via EAS I believe.  But that's a separate conversation - for now I'm curious about how to fix the conflict message and why it's showing up in the first place.

Hey all.  Normally when you see this it's because the client has changes on a message that the server also reported changes against.  As a simple example, Outlook marks an email as read and an EAS device flags it.  If the timing is right you could see a conflict like this and the client wants you to resolve it.  I'm not able to reproduce it on my end, however, Outlook has a "Folders" view that may help resolve the conflict.  You'll find the "Folders" view at the bottom left of Outlook, where you click on Email, Calendars, etc., you'll see a "..." menu that has the view.  After you switch to the "Folders" view you might see a "Conflicts" folder right above the account name, or you can see it under the "Sync Issues" folder.  I believe there you can attempt to resolve the conflict.

Strange, I have an account with EAS and MAPI with O365 and I've never seen this icon.

I think it's rare to happen against an exchange server.  I've seen it happen early on with our MAPI development but haven't come across it lately.  It could depend on the user's mailbox size in combination with other protocol factors.

It happened to me just downloading my mailbox. 

It also happened multiple times to me when I was giving MAPI a test drive from Outlook (201) and without any other device connected to this account (except the webmail for testing sync between the webmail and outlook/mapi)

It's the first time I discover this outlook conflict resolution feature. 

For history, we are using  an on-promise exchange server for our own domain for more than 6 years, accessing our mailboxes from multiple devices and even with multiple people accessing the same mailbox, we neved had to resolve a conflict on an object.

it looks a bit strange to me that it happens when accessing a mailbox with only one mail client and the webmail.

Ok, so it seems to happen even when there are no external modifications to emails.  This feels like maybe a timing issue or some sort of bug in our MAPI server code.

Do any of you recall what you were doing with Outlook when you noticed this conflict?  For instance, where you just letting Outlook sit there while it was syncing, were you clicking on emails and marking them read while it was syncing, or maybe sending out new emails, etc.?  Knowing what was going on during the sync may help us figure out how to replicate the issue.

It could even be tied to some meta data on the particular folder that's being synced or even a specific email.

I wasnt using Outlook at all, it simply downloaded all my email, I opened a few folders and noticed the icon.

Example... Fresh Outlook install, email has been marked as read for a week now, all I did was add the account to Outlook, I didnt send anything, didnt touch it at all other than when it finished syncing, I click around a few folders looking for conflicts. Note, that I sync'd this account about a week ago in testing, there were no conflicting messages then in this folder, so I am not sure how it determines that, but something seems odd. 

Hey Chris, can you try removing the profile from Outlook, then go into webmail and remove MAPI from your user's connectivity tab, then add the account back into Outlook.  See if you still get any conflicts when you do a fresh sync.

Just tried that, brand new Outlook install on a brand new Windows VM, removed the previous Outlook from SmarterMail, added it to the new installation and conflict icons are showing on different emails that previous ones, seems like it just randomly picks and chooses.

Ok, thanks.  Can you perform that same test again on the next build that we release.  Is far as I know it should be released tomorrow.  We have some changes coming that may affect what you're seeing with the conflicts icon.

If it's still not resolved after that test, then maybe I can get a fiddler trace from you to get a better understanding on what that account is doing.  We may have to go even further and get that user's account to troubleshoot locally, or remote into your server to gather information on the account.  We'll cross this bridge if we need to though.