Outlook Mailbox Full - Clearing out old emails

Outlook mailboxes can store up to 49.5GB of emails by default, and thus will need manually clearing out as Outlook will not delete any emails automatically no matter how old they are. This can also easily fill up if emails contain many attachments or large attachments, as they are included in this limit. This guide will only cover Outlook Classic.

To see your current mailbox storage, check File --> Mailbox Settings. I have 48.6GB free

To clear up your mailbox, you normally have 3 options

1. Remove old emails
2. Remove emails with attachments larger than i.e. 5MB
3. Remove all unsent drafts

Important - We keep a comprehensive email archive record of everything sent & received to all inboxes beginning March 2018. Everything after then can be found upon a request to IT, so don't worry about keeping anything 'just in case' you need it in the future. If you are unsure of performing the below actions, let us know and we will help!

Option 1 - Using the Mailbox Clean-up tool (Simplest)

File --> Tools --> Mailbox Clean-up

Click Find in the second section and this will bring up the search tool. Click on the Advanced section to open the search criteria entry. To add a criteria, begin with the Field dropdown menu. I will refine my search to look for all emails received in 2024 and are larger than 1mb in size.

Filter #1 - search all emails in 2024

Filter #2 - search for anything larger than 1MB (This value is in bytes, see link to convert megabytes to bytes MB to Bytes Conversion Megabytes to Bytes Calculator)

Once these are both selected by pressing the Add to List button, Click Find Now to perform the search. Note - This will search & return both Sent & Received items, even if it says just Received.

Then, you would select one of these emails, press Ctrl + A to select all and then right click --> delete to move all the items into your Recycle bin, at which point you can then remove them all from the Recycling bin to permanently remove them

Option 2 - Criteria in the Search bar

The below is the criteria to use in the search bar at the top of Outlook. 

(size:>1048576) AND (received:>=01/01/2024 AND received:<=31/12/2024)

Like above, this will scan for items matching the criteria of being within 2024 and being larger than 1MB. You'd just then select one --> Ctrl + A to select all --> Delete --> then remove once again from deleted items

But unlike the above method, you will also have to do this in Sent Items, as this search does not automatically include both sent & received items