Mailboxes have a storage limit, so to avoid getting warnings or errors (example shown below) you must carry out regular housekeeping.



Here are a few tips to help manage your mailbox size.


  • Attachments in emails take up storage in your mailbox, so rather than add an attachment share a link instead.
    See article Using links instead of attachments

  • Tackle emails with attachments first due to their size, in your folder view (be that Inbox, Sent Items or a custom mail folder) add a size column and sort mail by size.

    Switch your reading pane off

    Then, if the size column is not present, right-click on an existing column and select Field Chooser

    Locate 'Size' from the list and drag to where you want the column to be, then click on the column heading to sort by size.


    Target those emails that are 5MB and above. Perhaps save the attachment, or if you wish the email itself, to your OneDrive. Or simply delete the email if it's no longer required.

  • If you have folders of emails that you know could be deleted after a period, then apply mailbox rules and retention periods.
    See article Mailbox rules and email retention

  • Sort your mail by date, and question do you need to retain emails that are older than x months or years?

  • Managers - remember that you should not be retaining CV's longer than you need to, delete any emails containing these from your mailbox.  A reminder on this policy;
    "You should only retain candidate information (inc. CV's) for up to six months after notifying unsuccessful candidates (or longer, if there is a clear communicated policy that we keep candidates CVs for future reference, even in this case this must be deleted after a year at most as data will be out of date).
    Applicants should be informed if we plan to keep their information after an interview."

  • Don't forget to empty your Deleted Items folder!



If you are unable to delete emails via the Outlook program, you can also access your mailbox via webmail https://outlook.office.com/  

In webmail, in the top-right section of the screen, click on the cog icon


A Settings window will appear

If 'General' does not appear, you may have to click on the “View all Outlook settings” on the right-hand side of the settings window:


Go to General > Storage


Here, you’ll be able to clear up Deleted items and other folders, either fully empty the folder or clear up emails older than 12, 6 or 3 months old.

As it says on this screen "Emptying contents from a folder will help free up space.  Items will be permanently deleted", so please proceed with caution.