Outlook 2016 Missing Emails with MAPI
Problem reported by Liam Dwyer - 9/17/2021 at 6:39 AM
Several users have been reporting recently that Outlook(MAPI) is not showing all the emails in their Inbox.  They had noticed that an email appears on their phone (EAS) but never arrives in Outlook.  The email appears just fine in the Web Client as well.

This is very sporadic and intermittent, but it is wide spread to pretty much every user.  I had them check the Synchronization status of their Inbox and compare the Server Folder Contains and the Offline Folder Contains and pretty much everyone is reported a difference - anywhere from 10 - 400 more emails on the server than in Outlook.  Outlook is set the synchronize the entire mailbox.

Windows Server 2019
SmarterMail Enterprise
Build 7887 (Aug 5, 2021)
Outlook 2016 MAPI (fully updated)

10 Replies

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Kyle Kerst Replied
Employee Post
Hello Liam, I'm sorry to hear you're seeing sync issues with these clients. What I recommend is first completing an upgrade to our latest release build 7929. Once the upgrade is complete, use these instructions to have the affected users re-sync their Outlook clients:

At that point please have them open up Outlook and let it sit for at least a few hours to complete its initial resync process. Please then have these users monitor for further issues, and submit a ticket on this if those issues persist so we can get this escalated as needed. Have a good one!
Kyle Kerst System/Network Administrator SmarterTools Inc. www.smartertools.com
Liam Dwyer Replied

I have updated to the latest version of SmarterMail.

I have completely removed the profile as per instructions.  Outlook fully synchronized.  After a few days Outlook was out of Sync again. There are more messages on the server (and visible in SmarterMail) than in Outlook.

After a week there are approximately 25 messages missing from Outlook.

Stefano Replied
Hello Liam,

have you also removed all the voices from your webmain under "Connectivity"?
You should close Outlook, remove profile, remove all that entries, readd the profile.
I'm using the MAPI and it's working fine for me.

Mike Mulhern Replied
Hi Liam---

We have a similar issue where an email can be present in SM webmail and EAS (iPhone) and not in MAPI > Outlook.  I have gone back and forth with SM for a few months but we/they have not been able to identify the problem.  Your issue might be the same as mine or different, I don't know.

SM feels it may be something in my environment but this isn't something I am sold on at the moment.

One experiment I ran is to have MAPI > Outlook 2016/2019 running on 3 different machines synced to the same SM Email Account.  All three instances of Outlook 'lost' messages but none of the 'lost' messages were the same in any instance.

The latest idea is that maybe the mailbox size has something to do with the problem.

I've shrunk the cache in Outlook to 1 month and ran two weeks to see if emails get 'lost.'  1 month cache has been stable for two weeks and I am now testing 3 month cache to see what happens.

How large are the mailboxes losing the emails?
Liam Dwyer Replied

Thank you for the response.  Good to know someone else is having a similar problem.  I have done similar troubleshooting as you have.  And I have had the same result.

My next step was to reduce the offline cache as well.  The mailboxes range in size from about 4GB to 10GB.  Not what I would call large.  The one other thing I have noticed is that it only seems to affect the Inbox folder.  Sent Items, Deleted Items (even though they are much larger in message counts) do not have any issues.

This is a client with over 100 users, all on Outlook 2016, so asking them to repeatedly remove and re-add profiles is NOT an option until a resolution is achieved.

Mike Mulhern Replied
All of our mailboxes are in the same range, 4gb to 10gb.  Interesting not in sent or deleted as I did not think to evaluate these.

I have the problem documented in maybe 3-5 users out of 60 but I suspect it's occurring to more users given the intermittent and subtle nature of the problem.

Once I have my 3 month cache test done I'll let you know how it goes.

Did you happen to open a ticket with SM?
Liam Dwyer Replied
I have not opened a ticket yet.  

I have also tested the same mailbox using emClient connected via EWS. And it appears to stay synchronized.

*UPDATED* I opened a ticket and referenced this thread.

Mike Mulhern Replied
HI Liam---

Outlook cache @ 3 months appears stable after 2 weeks.  I will move to testing 6 months next.  Please let me know if you have any progress on your end.  Thanks.
Mike Mulhern Replied
Liam, cache @ 6 months and emails start to be missing in Outlook.  I'm guessing that once the amount to cache is a certain size SM > MAPI > Outlook is having problems.  Have you had any luck with your ticket?
Liam Dwyer Replied

After all the usual instructions; recreate the profile, etc they are going to try to sync to one of the problematic accounts from their Outlook to investigate further.  I'm not overly optimistic.   The client is now trying to decide whether they are willing to move off Outlook, or whether they will switch to O365 :/

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