In this guide we are going to cover the steps needed when expanding shared mailbox size.

The Problem

The users of a shared mailbox were being notified that their mailbox was about to be full.  They were receiving messages informing them with this message:

“Please reduce your mailbox size. Delete any items you don’t need from your mailbox and empty your Deleted Items folder.”

Expanding Shared Mailbox Size

Now in our environment, we have shared mailboxes stored in Office365 and user mailboxes stored on premise.  So this fix was not as easy as just accessing the ECP and changing the mailbox size.

In order to fix this issue we will be expanding the shared mailbox size by modifying the quota via Exchange Online.

The Fix

The first part is accessing Exchange Online since this is where the mailbox is stored in this instance.

To connect we will do the following steps:

Step 1 – Open Windows Powershell

Step 2 – Get Connected to Exchange Online

Next we are going to store our credentials in a variable.

Type the following:

$cred = Get-Credential

Powershell - Get Credential Variable

When the credential popup opens, enter your email address and password.

Powershell - Get Credential Popup

***Please note that the account attached to the email address specified must have the correct permissions!***

Now that your credentials are stored type the following:

$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri -Credential $cred -Authentication Basic -AllowRedirection

Powershell - Store Session Variable

Now that the session is stored into the variable we can connect to Exchange Online

Type the following:

Import-PSSession $Session

Powershell - Import Session

Make sure that your Execution Policy will allow our next script to run. If you are unsure of what it is currently set to, you can type: Get-ExecutionPolicy.

If your Execution Policy settings are restricted, then you will get an error like the one below.

Powershell - Import Session - Execution Policy Failure

Set the Execution Policy to unrestricted by typing:

Set-ExecutionPolicy Unrestricted

Powershell - Set Execution Policy Prompt

You will need to accept the change by pressing Y and hitting the enter key.

Now running our Session Import works as expected!

Powershell - Import Session Success

Step 3 – Expanding Shared Mailbox Size

Now that we are connected, we can expand the shared mailbox size by typing out the following command:

Set-Mailbox Username -ProhibitSendQuota 48GB -ProhibitSendReceiveQuota 49GB -IssueWarningQuota 47GB

Make sure that the value of ‘ProhibitSendQuota’ is less than or equal to that of ‘ProhibitSendReceiveQuota’ which is the new mailbox size.  I usually set ‘IssueWarningQuota’ to be 1GB less than the ‘ProhibitSendQuota’