Managing your Outlook mailbox size
For Office 365 Exchange email, the maximum size of your mailbox is 50GB. Here’s what to do when you’re approaching the limit.
Understanding your mailbox size limit
For Office 365 Exchange email, the maximum size of your mailbox is 50GB. 50GB is also the maximum file size of the Outlook data file (OST) stored on your computer.
Your mailbox increases in size over time primarily due to attachments you send and receive. When you get notifications about your mailbox being close to the maximum limit, please let us know.
We will get onto your computer and run a process that relocates attachments from Outlook. You will still be able to access the attachments — they will just be stored elsewhere and linked to Outlook.
Ensure Outlook is fully synced with Exchange
Before we process your attachments we need to make sure your Outlook is set to fully sync with Exchange. To do this:
On the File tab in Outlook
Click Account Settings, then click Account Settings again.
On the E-mail tab
Double-click your Microsoft Exchange account.
In the Change Account dialog box
Drag the Mail to keep offline slider to the desired number of months or to All to synchronise all email messages.
Click Next, then OK
When prompted, restart Outlook to complete the configuration change.