What Outlook for Mac users can do when their Exchange mailbox is full?

Siddharth Rawat
Siddharth Rawat | Updated On - 09 Apr 2021 |

Read time 4 min

Outlook for Mac accounts connected to Exchange may sometimes get error messages stating that their Exchange mailbox is full. And IT support team may have to ask the email client users to delete unnecessary emails and attachments or to archive their mailbox data. Here, we will go through the causes of this issue and the ways to deal with it.

Why is the Exchange Mailbox Full?

An Exchange-connected user mailbox cannot accommodate more messages than the mailbox quota allocated by the Exchange administrator for it. The prominent reasons for the filling of Exchange mailbox are duplicate items, large-sized emails, and their attachments. The consequences of a bulky Exchange mailbox are corrupted database files, downtime, slow performance, or data loss in severe conditions.

These effects are undesirable, and so, users will have to reduce their mailbox size from the Outlook for Mac email client itself. Deleting unwanted emails and separating attachments from mails can help to some extent. However, a better approach would be to archive the old Outlook for Mac mailbox data and retain only the recent and most relevant items in the mailbox. Let us see how you can check the size of your Outlook for Mac mailbox folders and archive their items.

Instant Solution

Get Kernel for OLM to PST Converter, an automated tool to backup your important Outlook for Mac user data, including emails, attachments, calendars, etc. to Outlook PST.

How to Check the Size of Mailbox Folders in Outlook for Mac?

In Outlook for Mac, users don’t have the facility to check the size of the entire mailbox. They have to do it individually for each folder. For this, right-click the folder, select Folder Properties, and go to the Storage tab on the Folder Properties dialogue box. Here one can view the size of the folder as well as the sizes of its subfolders.

How to Archive Outlook for Mac Mailbox Folder Data?

The method for archiving folders in Outlook for Mac is given below:

  1. Begin by choosing one or more messages to archive.
  2. From the top ribbon, select Archive.
  3. Click on Continue on the prompt (this will let you create a new archive folder).
  4. Now, to set archiving rules, go to Tools and select Rules, further select Edit Rules.
  5. Then select Exchange from the left menu pane, then click on ‘+’ to add a new rule.
  6. Assign a Rule name and specify the required conditions. Then click on OK to save the rule.
  7. To apply the rule to a folder, select all its emails and click Message > Rules > Apply > Select Rule.

How to Backup OLM Files in PST?

Many OLM users may want to backup their OLM files as PST files. By doing so, they can access their emails in MS Outlook (Windows environment). The process is given below:

  1. Launch the Outlook for Mac application. Go to the Outlook menu and then click on Preferences.
  2. Follow Tools>Accounts.
  3. Click on the Add email account option.
  4. Start by signing in to your Gmail account so as to configure the IMAP email account.
  5. Then configure your Mac Outlook OLM file with the same Gmail account.
  6. Now, create a Gmail label and then start synchronizing the OLM file with IMAP
  7. Now, move all OLM file data to the IMAP account and then move OLM emails from IMAP mailbox to MS Outlook PST by configuring that IMAP account in the Outlook client application.

Also, you can opt for a third-party tool, Kernel for OLM to PST converter for the conversion of OLM files to PST. This tool helps you to convert OLM files to PST format. It helps migrate all Outlook for Mac items, including emails, attachments, calendars, etc., to the Windows environment. With this tool, you can also save Outlook for Mac emails to various destinations like Exchange Server, Office 365, Gmail, MBOX file (Apple Mail), etc. For the conversion, you just need to transfer your OLM files to a Windows system with Kernel for OLM to PST. After the conversion to PST, you can access the data in MS Outlook.


The blog was focused on the issues generated due to a bulky Exchange mailbox in Outlook for Mac. Some manual practices like archiving, data transfer, or backup are explained; for fully automatic conversion of OLM files to PST, a smart solution is introduced in the end.