We've got a user that's having random sent messages disappear after sending, they aren't stuck in the Outbox and they never reach the recipient. This used to occur on our Exchange 2007 server but we've since moved to Exchange Online; the problem remains. This only happens with Cached Mode enabled, disabling is too slow with O365.

We use Webroot for AV, but they haven't been able to find an issue with their software. The user is on Outlook 2013 and it's up-to-date.

Any suggestions?

closed as off-topic by Ward, HopelessN00b, Sven, TheCleaner, mdpc Dec 1 '14 at 22:42

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  • I would suggest adding more information about what you've already done to track down the problem; as it is there's not a whole lot to go on. – Michael Lowman Dec 1 '14 at 3:01

Sadly i cant add a comment yet, so i have put my suggestion in here.

Have you checked the Get-MessageTrackingLog to see if it shows any record of the email or delivery reports in ECP?

Do you have any mail flow restriction rules in place that might be affecting this user?

There are a lot of potential issues here, but the fact that its affecting the same user may narrow it down to specific settings or issues on there machine.

you say it kept happening on Exchange 2007 as well as O365, was the user using the same workstation for both email systems?

Cached mode stores its data in .OST files, these can get corrupt, i would suggest

turning off cached mode.

deleting the .ost files (located at C:\Users\username\AppData\Local\Microsoft\Outlook on windows 7)

turn on cached mode. (email data will need to downloaded again so many need to choose a convenient time for the user to do this)

let me know how you get on.


  • Hi, I can't use Get-MessageTrackingLog as it's not available with Exchange Online. It was the same workstation for both mail systems, and to think back it was affecting the previous user of this PC prior to the current user. – s-twig Nov 27 '14 at 22:46
  • sounds like it could be a local issue on the workstation then,if the option exists could you do a clean OS install on the workstation? – GordonBpdZenith Nov 28 '14 at 8:57
  • also can you not access message tracking from the Exchange Admin Center > Mailflow > Message Trace? – GordonBpdZenith Nov 28 '14 at 9:10
  • Exchange Online/O365 does allow for Get-MessageTrace or similar like Gordon's last comment here. They also offer free support, so I'd suggest opening a ticket with them on this user. Gordon's "answer" is decent enough to not be converted to a comment by the mods IMO. You can also check Outlook's sync issues folders. I would also check OWA's Sent Items folder for the user. The OP's question isn't detailed enough though for an expert here to pinpoint the issue without detailed discussions. – TheCleaner Dec 1 '14 at 20:19

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