Office 365 – Shared mailbox sync issues

I have been using shared mailbox for the majority of customers running Office 365 for a long time.Its a great way to create a mail-structure for different type of groups in an organisation.

For exampel,, so on and so forth.
This is completely free, but to access this “Shared mailbox” you need an Office 365 account with an valid license and a outlook 2010+ client installed.

However, i’ve seen a couple of issues with “Shared mailbox” as well.
Several customers have reported that they don’t get regular updates in the shared mailbox. In some case, the mailbox is not updated in several days for some users.

This is a known issue, its a bug in the “Automapping” function that make the shared mailbox automapp in the outlook client.

Here is one way to solve the issue:


Step 1:

Remove the users “Full permission” to the “shared mailbox” witch isn’t syncing.

Step 2:

Make sure the “Shared mailbox” disappears from the users outlook client.
(You might speed up the process by restarting outlook.)

Step 3:

Disable the automapping function and add FullAccess to the specific shared mailbox through powershell:

Add-MailboxPermission -Identity “shared mailbox name” -User ‘Users name’ -AccessRight FullAccess -InheritanceType All -Automapping $false

Step 4:

Add the shared mailbox manually through the following steps:

Right-click on your main account and select “Data file properties” -> “Advanced” -> “Advanced” -> Press “Add” and type the emailadress of the “shared mailbox


The mailbox will now start to sync as it should.
Be aware of “Use cached exchange Mode” This might take up alot of disk space in the user profile disk or on C:\ depending on setup and environment.

1 thought on “Office 365 – Shared mailbox sync issues

  1. Michael Walsh

    Thanks for this. After everything working fine with out O365 for about 3 years, 8 months ago I started having problems with users losing shared mailboxes created in the O365 admin console and was pulling my hair out. Things settled down after about 2 months of hell, so I shrugged it off, but it just started happening again. No rhyme or reason to it that I see, but I’ve just added a shared mailbox back to a users Outlook using this method and it seems like it might be a solution for me (fingers crossed).



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