Emails delayed showing up  in Outlook Inbox

namits used Ask the Experts™

I hope someone can offer a few thoughts. I'm having problems with emails arriving in the Inbox for several clients.

There are 5 people accessing a shared mailbox in the same physical office. Some have the mailbox setup as their main account whilst others have multiple accounts all setup as individual account, not accessed via share permissions.

Clients are using a mix of Outlook 2010 and Outlook 2013. All operating systems are Windows 7 64 bit fully updated

All systems are running ESET Endpoint Antivirus

Mailboxes are hosted on Office 365

For one user emails arrive with no issue, user is running Office 2010

For the other users an email arrival notification message will be shown and the mail can be opened from the notification. You can then reply to the email and replies will show up in the sent items. After closing the email it cannot be seen in the Inbox.

For some users the emails will all finally arrive in the Inbox hourly in a batch. Other users could go a whole day with nothing arriving.

Things I have tried or tested

Rebuilt all of the Outlook profiles
Tried with and without cached mode
Tested as single mailbox, primary mailbox with additional mailboxes and as the secondary mailbox
Reinstalled office
Tested internet speed and access to mailbox
Tested through OWA with no issues
Disabled email scanning on ESET
Fully disabled ESET AV
There are no rules setup in any of the Outlook profiles

There are other teams in the office accessing similar mailbox setups with no issues

Any ideas about a fix would be most appreciated
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If only users in that particular location are having issues, I'd say look at network performance. Probably the best test you can make is to get one of the affected users to try from a different location, if those are laptop users connect them via some WiFi network or similar. It might as well be something related to the local user account or additional software installed on their machines, so try to test those scenarios as well.

Other than that, the usual suspect is large mailbox size. You have pretty much checked every combination, but if the size of said mailbox is too large try to simply bring it down a bit - either clean up older mails or setup an Online archive for it.

OWA is also an option when it comes to shared mailboxes.
namitsIT Consultant


Hi Vasil

Thanks for the reply. I'll have a look at your suggestions.


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