Microsoft Mailbox Size Limits and Archiving Email

By default, Microsoft 365 licenses include storage capacity for up to 50GB of email (or more depending on which license you have). This includes all email folders (Sent Items, Deleted Items, etc).

When you get near this limit, you'll receive an email from Microsoft telling you as much

If you don't clean up your mailbox and you hit its limit, you will be unable to send email, and any emails sent to you will bounce back to the sender. To see how much of your mailbox you're using (and which folders are taking up the most space), you can click this link:

https://outlook.office.com/mail/options/accounts-category/storage

So, what do I do?

Your Microsoft account includes a separate mailbox called the In-Place Archive mailbox. This mailbox has its own size limit (by default 50GB) that is separate from your regular mailbox. You can (and should) move your old emails into this In-Place Archive mailbox to prevent your mailbox from getting full.

System Admin Pro Tip #1: Ideally, it's best to not keep emails forever, particularly ones with large file attachments. As a whole we've come to view email as another kind of file storage, which is a bad habit to have (particularly when you have mailboxes with storage limitations). Saving emails/attachments to project folders (or your OneDrive folder), deleting redundant emails (like things you've scanned to your email account and have already saved the PDF somewhere), deleting "there are donuts in the conference room" emails, etc., are all good habits for having a tidy mailbox. I set aside a few minutes each morning to remove any items I don't need, and do my best to do so during the day as well—identifying non-essential emails (vendor sales inquiries, etc) is pretty immediate, so I can whack them pretty quickly.

There are two ways to move items to your In-Place Archive: manually moving items and using pre-configured retention policies.

System Admin Pro Tip #2: If you're using the Legacy Outlook, items placed in your In-Place Archive folder will not show up in a default mailbox search as the search is running against your active mailbox, not the In-Place Archive mailbox. Legacy Outlook users will need to click the down-arrow next to the search box and select All mailboxes to include the In-Place Archive mailbox folders in their search.

If you're reading this, it's possible your mailbox is almost full, so you'll want to do some manual cleanup for some immediate relief (then you can set up your retention policies for more advanced cleanup/making sure you're good moving forward).

Manually moving emails to your archive mailbox

For the sake of brevity, if you're going to move emails manually from your mailbox (which you'll need to do if your mailbox is currently full) you'll want to do this using the web-based Outlook email client. The main reason for this is using your desktop client to move emails will result in tying up the program with the move process, preventing you from using Outlook for your normal email tasks until it's done. Using the web-based Outlook however allows all this happen on the server side, freeing you to work in your desktop Outlook app normally. In addition, this will ensure that a Legacy Outlook user has access to all of the emails in their mailbox (as most Legacy Outlook deployments only have 6-12 months of recent mail displayed).

1. First, log into https://outlook.office.com/mail to access your mailbox.

2. Once logged in, scroll down to the end of your email folders and you should see your archive mailbox labeled In-Place Archive.

   
   

   

   
   
3. Expand this mailbox and you can create whatever folder hierarchy you like. You cannot drag and drop entire folders into the Archive mailbox, so you'll want to create your folder first.
4. Once created, you can then navigate to a folder in your normal mailbox, select your emails, and drag/drop them into the folder in the Archive Mailbox. Alternatively, you can right-click on the emails after you've selected them, then select Move -> In-Place Archive. You'll be presented with the folder list of your In-Place Archive mailbox and can select the folder where you want the messages to be moved. Selecting the folder should start the move process. If there are a LOT of emails to be moved they make take some time to disappear, but at any rate using the web-based Outlook will allow you to immediately continue working on moving other emails to other folders.

Using Pre-configured Retention Policies

If you're not in any immediate trouble with your mailbox size, you can apply some pre-made retention policies. These policies have been created by IT to assist in moving things to your In-Place Archive in the background.

We currently have policies to move items to the In-Place Archive mailbox if they're older than 1 year, 2 years, 3 years, 4 years, or 5 years. You can set these policies on a per-folder basis. By default, setting the policy on a parent folder will also apply it to all sub-folders, but you can go into a subfolder and change the policy for that sub-folder (and its sub-folders) to a different one if you want.

The move will not be immediate. The system process that runs in the background runs once per week, so it will be up to 7 days before you see the message leave your mailbox and show up in your In-Place Archive. The process will create the folder structure on its own, putting the folders in the same relative location as they are in your primary mailbox.

To apply an Archive policy (using the New Outlook, or using Outlook on the web):

1. Locate a folder you want to apply a policy to.

2. Right-click the folder, select Assign policy, and select the Archive policy you want to assign. If you don't see Assign policy then you're probably using Legacy Outlook, and will use the steps in the next section.

   
   

   

   
   
3. That's it! Within the next 7 days the items in the folder that match the policy will be moved out of your mailbox and into your In-Place Archive mailbox.
4. Repeat this process for any other folders you want to automatically archive.

To apply an Archive policy using legacy Outlook:

1. Locate a folder you want to apply a policy to.

2. Right-click the folder and select Properties at the bottom.

   
   

   

   
   
3. Click on the Policy tab.

4. Under Online Archive, click the drop-down and select which Archive Policy you want to assign.

   
   

   

   
   
5. That's it! Within the next 7 days the items in the folder that match the policy will be moved out of your mailbox and into your In-Place Archive mailbox.
6. Repeat this process for any other folders you want to automatically archive.