Reducing the Size of your Mailbox

At Dartmouth, each mailbox within the O365 (Outlook) environment has a limit for the amount of data that can be stored within it. We refer to this as the Mailbox Quota. That quota varies by mailbox but for most will be 100 GB. If you exceed the quota, you will no longer be able to send e-mail from your account.

On this page, we provide you with various strategies to reduce the size of your mailbox. While your mailbox is in one location, people use many different tools to access their mailbox. The tool you use will determine how you can keep your stored data below the quota. From the list below, choose the application you use:

Outlook on the Web (o365.dartmouth.edu)

The quickest way to determine the size of your mailbox in Outlook on the web is to click on the gear in the upper right corner and choose Options. Click My Account under the General section. You should see a progress bar with your mailbox usage. Remember that you may have multiple accounts to check – your account, your department's account, accounts set up for processing, etc.

If the mailbox size on any of these accounts is too large, there are a few steps you can do to remedy this situation:

• Empty your Deleted Items and your Junk E-Mail folders. Many people don't realize that messages in your "Deleted items" and "Junk E-Mail" folders count towards the total size of your mailbox. If you no longer need a particular message, it makes sense to empty these folders to quickly reduce the size of your mailbox. To do this, first, make sure there is nothing in the folder that you will need. Next, using Outlook via o365.dartmouth.edu, right-click (or Ctrl-click on a Mac) your Deleted Items or the Junk E-Mail folder, then choose Empty Deleted Items or Empty Junk E-Mail from the menu that appears. Click Yes. If you have a lot of items, it make take a few extra seconds to complete the deletion.
• Remove large messages that you no longer need. Sometimes you'll receive messages with images embedded in the message which makes it relatively large. You can easily find these messages, then delete if appropriate, by sorting the messages in each folder by size so the largest ones appear at the top. Do this in Outlook on the web by selecting the folder in which you want to search and then choosing Size from the sorting drop down. The sorting drop down list is located just above your list of emails and just below the search box. Scan through the list of your largest messages, deleting ones you no longer need. Remember to empty your trash once you delete any of these large messages.

Outlook 2016 (Windows)

The quickest way to determine the size of your mailbox in Outlook 2016 is to click the File tab. On the Info screen is an indicator showing you how much free space you have remaining. Remember that you may have multiple accounts to check – your account, your department's account, accounts set up for processing, etc.

If the mailbox size on any of these accounts is too large, there are a few steps you can do to remedy this situation:

• Empty your Deleted Items and your Junk E-Mail folders. Many people don't realize that messages in your "Deleted items" and "Junk E-mail" folders count towards the total size of your mailbox. If you no longer need a particular message, it makes sense to empty these folders to quickly reduce the size of your mailbox. To do this, first, make sure there is nothing in your trash that you'll need. Next, using Outlook 2016, right-click your Deleted Items or Junk E-Mail folder, then choose Empty Folder from the menu that appears. Click Yes.
• Remove large messages that you no longer need. Sometimes you'll receive messages with images embedded in the message which makes it relatively large. You can easily find these messages. Click the Search box, located directly above your list of email. The Search ribbon should appear; in the Refine group of the Search tab, choose More. Select Message Size from the list that appears and enter in the size of the email messages that you'd like to find that are larger than that number. (For example, if you would like to see only emails whose size is greater than 1 MB, then enter: >1 MB). Be sure to enter the greater than sign, otherwise you'll be looking for messages that are of the exact size that you entered. Make sure Current Mailbox is selected as the location to search and press Enter. If your search does not return everything that you think it should, scroll to the bottom of the results and click More. Scan through the list of your largest messages, deleting ones you no longer need. Remember to empty your trash once you delete any of these large messages.
  
  Alternatively, you can sort each folder in your account by the size column so the largest ones in that folder appear at the top. Do this in Outlook 2016 by clicking Size found in the menu bar at the top of the list of messages. Note: If you don't see the Size column you can widen the content pane or right-click the header and choose Size from the menu. Scan through the list of your largest messages, deleting ones you no longer need. Remember to empty your trash once you delete any of these large messages.
• Remove attachments from messages that you have already stored elsewhere. Often when someone sends you an e-mail messages with something attached, you save the attachment to your computer. In many instances, once you've done this you no longer need to keep a copy of the attachment in your mailbox. In Outlook 2016, you can easily find these messages across all folders within your account using the Search box. Click the Search box, located directly above your list of e-mail. The Search ribbon should appear; in the Refine group of the Search tab, choose Has Attachments. Make sure Current Mailbox is selected as the location to search and press Enter. If your search does not return everything that you think it should, scroll to the bottom of the results and click More.

  Alternatively, you can sort each folder in your account by the size column so the largest ones in that folder appear at the top. Do this in Outlook 2016 by clicking the paperclip icon found in the menu bar at the top of the list of messages. All messages in that folder with attachments will appear at the top of the list.

  Unfortunately, there is no good way to globally remove attachments. You'll need to open each message, right click the attachment(s) then select Remove attachment from the menu that appears.

• Create an archive of older messages that you don't refer to often but don't want to lose. In some instances, it is important to not delete messages and/or to keep the e-mail message and attachment together. Archiving places your email into an Outlook Data File (known as a PST) and removes the email, along with any attachments, from your mailbox. It is important to note that folder properties such as permissions are not preserved when you export messages to a PST file.

How to archive to an Outlook Data File (PST) in Outlook 2016

1. 1. Using Outlook 2016, log into the account from which you want to create the archive.
   2. It is a good idea to empty your deleted items (See Empty your deleted items, above) before going any further, as items in the deleted items folder will be archived.
   3. Click the File tab, click Cleanup Tools and choose Archive.
   4. Select the option to Archive this folder and all subfolders.
   5. Select the account – a top level folder – that you want to export. (e.g. firstname.i.lastname@dartmouth.edu) Usually that is your email address. This will cause all mail, calendar, contacts, tasks and notes that meet the criteria you specify to be archived.
   6. Choose a date prior to which you would like your items archived from the Archive items older than dropdown box.
   7. Make sure that Include items with "Do not AutoArchive" checked, is checked.
   8. Click Browse and navigate to where you want to save the archive (PST) file. Enter a name for the file to be created. If you select a PST that already exists, the archival process will append the new data to the data in the existing PST file.
   9. Click OK.
   10. As soon as you click Finish the archiving will begin so make sure you have your criteria set correctly.
   11. You should be able to view your archived items by looking in the "Outlook Data File" entry in the navigation pane on the left side of your Outlook window
   12. We recommend that, if you don't need this archive always and immediately available, that you right-click on it in the navigation pane, to then close the Outlook Data File. Once you have done that, you can move the file to somewhere that it will be regularly backed up. Then, if the need arises to access those messages in the future, you can point Outlook 2016 at that file and open the messages as if they were stored on your computer.

Outlook 2016 (Mac)

The quickest way to determine the size of your mailbox in Outlook2016 is to Ctrl-click on your account name (Usually "Dartmouth") in the folder list to the left of your list of emails and choose Folder Properties. At the top of the dialog box, click the Storage button.  After a few moments you should see a number associated with "Total size (with subfolders)". Remember that you may have multiple accounts to check – your account, your department's account, accounts set up for processing, etc.

If the mailbox size on any of these accounts is too large, there are a few steps you can do to remedy this situation:

• Empty your trash and junk mail folders. Many people don't realize that messages in your "Deleted items" folder and "Junk E-mail" folder count towards the total size of your mailbox. If you no longer need any messages in those folders, it makes sense to empty them to quickly reduce the size of your mailbox. To do this, first, make sure there is nothing in your "Deleted Items" or Junk Email" folders. Next, Ctrl-click on your Deleted Items folder then choose Empty Folder from the menu that appears. Click Yes. Next, Ctrl-click on your Junk Email folder then choose Empty folder from the menu that appears. Click Yes.
• Remove large messages that you no longer need. Sometimes you'll received messages with images embedded in the message which makes it relatively large.
• Remove attachments from messages that you have already stored elsewhere. Often when someone sends you an e-mail messages with something attached, you save the attachment to your computer. In many instances, once you've done this you no longer need to keep a copy of the attachment in your mailbox. 
  
  Unfortunately, there is no good way to globally remove attachments. You'll need to open each message, right click the attachment(s) then select Remove attachment from the menu that appears.
• Move older messages to your "On My Computer" area. In some instances, it is important to not delete messages and/or to keep the e-mail message and attachment together. Moving the e-mail to a folder in your "On My Computer" area, removes the e-mail, along with any attachments, from your mailbox. These messages will no longer be stored in the cloud so you should be certain that you have a backup strategy.  Note: If you do not see "On My Computer" in your folder list, do the following: From the Outlook menu choose Preferences. Under Personal Settings, choose General. Remove the check for the Hide on My Computer folders checkbox.

Apple/Mac Mail (Mac)

Within Apple Mail there is no simple way to determine the amount of data that you have stored in your mailbox. You should log into your account using Outlook on the Web (o365.dartmouth.edu) to find that information. Once you have logged in to Outlook on the web, hover your mouse over your account name in the folder list on the left side of your Outlook window. Remember that you may have multiple accounts to check – your account, your department's account, accounts set up for processing, etc.

• Empty your trash an junk mail folders. Many people don't realize that messages in your "Trash" folder and "Junk E-mail" folder count towards the total size of your mailbox. If you no longer need any messages in those folders, it makes sense to empty them to quickly reduce the size of your mailbox. To do this, using Apple Mail, first move any items in your Junk E-Mail folder into your Deleted items folder. Don't move the folder, just the items in the folder! Next, from the menu choose: Mailbox, select Erase Deleted items and then choose the account (usually "Dartmouth") from which you would like to empty the deleted items. Click Erase.
• Remove large messages that you no longer need. Sometimes you'll received messages with images embedded in, or files attached to them, which make the message relatively large. (Apple Mail treats embedded graphics exactly the same way as attachments so if you remove just the attachment, any images or graphics embedded in the e-mail will also be lost.)

In Apple Mail, removing messages with embedded images or attachments can easily be done across all folders within your account using a "Smart Mailbox". Smart Mailboxes provide different groupings of the messages in your account.

To create a Smart Mailbox:
a) From the Menu bar click Mailbox.
b) Click New Smart Mailbox from the menu that appears.
c) In the Smart Mailbox Name field enter the name you want for this new view of your messages. (e.g. E-mail with Attachments and Images).
d) In the first row where you specify what to include, in the first field, select Contains Attachments from the drop down list.
e) Place a check in the Include messages from Sent field.
f) Click OK.

In the left navigation bar of your Mail window, click the new Smart mailbox you just created. Any messages with embedded image or attachments will be displayed. Click the Sort by drop down found just above your list of emails, then click Size from the menu that appears. Delete any messages you no longer need. Remember to empty your trash once you delete any of these large messages.

Alternatively, you can sort each folder in your account by the size column so the largest ones in that folder appear at the top. Do this in Apple Mail by clicking Sort by drop down found just above your list of emails. Scan through the list of your largest messages, deleting ones you no longer need. Remember to empty your trash once you delete any of these large messages.

• Create an archive of older messages that you don't refer to often but don't want to lose. In some instances, it is important to not delete messages and/or to keep the e-mail message and attachment together. Archiving places your e-mail into local storage on your Mac and removes the e-mail, along with any attachments, from your mailbox.

To create an archive in Apple Mail:
a) From the menu bar click Mailbox, then New Mailbox.
b) In the Location field, select On My Mac and then give the new mailbox a name (e.g. "Messages for 2012").
c) Your new mailbox should now appear, along with your other mailboxes, in a section called "On My Mac". Any messages that you move to this folder will be removed from your cloud account and stored locally.

Important: Since these messages are no longer stored in your mailbox on remote servers, make sure your computer is backed up so you don't lose the message you moved to the "On My Mac" location.