I thought I had previously read that only a single MAPI sync per mailbox was supported which may explain why you only see it once. 

We have been licensed for MAPI for 2 years but do not use it yet as there seems to be constant issues so i cannot confirm if we experience the same.

It is normal.  All protocols are different.  

I have searched and not found anything indicating that MAPI would only sync a single device on a mailbox or even only sync one device at a time.

Could someone at ST provide a  heads up if there is a sync limitation please.

I'm not sure what you are saying?

Outlook can connect to one or more MAPI accounts.

One mailbox can have multiple Outlooks MAPI's connected.

What's in Sync devices doesn't really matter and we may be removing some of what you see in the near future.  

Thanks Tim.  The post you responded to directly above yours suggested that "only a single MAPI sync per mailbox was supported" and you didn't take issue with it.  I hadn't heard of the limitation before so thought I'd better check.

@Tim: "It is normal.  All protocols are different."

"In case I need to completely replace a MAPI account ( as per https://portal.smartertools.com/kb/a3487/how-to-thoroughly-replace-your-mapi-account.aspx ) because it has a problem while the others are okay, am I obliged to reset them all?

Or can I safely reset the broken one only?"

Thanks in advance!

Is a new Windows install better than an upgrade.  Heck yea!  Same is true with Outlook.  Outlook leaves crap all over the place and the best way to make sure there are no cached files and resources is to remove and re-add a profile by following our KB.  This will also solve the most common issues with Outlook: corruption, bad sync states and deep rooted issues in Outlook itself.

If you have three Outlooks connected to a single mailbox and only one Outlook is having an issue and you have access to that client... I would have them remove and re-add the profile so the other two Outlook clients and other clients (EAS, EWS, DAV) don't do unnecessary work.

"Resync all Devices" should be used:

when clients have are generally heathy;

when you want to data refresh all clients;

when you don't have access to the client and want to try to fix;

"Resync all Devices" shouldn't be used:

when your client is really messed up;

when you have a ton of clients connected to a mailbox with limited bandwidth;

when your concerned about server bandwidth;

when you have access to the client and can reset it on the client;

I can go on and on but I hope this helps.

And this applies to EAS, EWS and a variety of clients.

Don't let the connectivity list really mess with you, its becoming a bit obsolete as we introduce more functionality.

THX for the advices, Tim!

"One mailbox can have multiple Outlooks MAPI's connected."

Hi Tim,

This reminds me, a while back doing this was a problem, however I didn't know if it was just a minor thing with an imminent fix or if it was more of a long-term issue.

"Two MAPI clients on the same account is an issue." <-- Am I correct in assuming that's no longer the case today? My user who uses two different Outlook desktop clients via MAPI seems to not be having issues anymore, though I have since recommended to him to try to only have one open at a time. Thanks!