{"id":145693,"date":"2023-08-14T12:03:44","date_gmt":"2023-08-14T12:03:44","guid":{"rendered":"https:\/\/www.stellarinfo.com\/blog\/?p=145693"},"modified":"2025-04-11T06:29:35","modified_gmt":"2025-04-11T06:29:35","slug":"how-to-fix-error-your-mailbox-is-almost-full-in-outlook-365","status":"publish","type":"post","link":"https:\/\/www.stellarinfo.com\/blog\/how-to-fix-error-your-mailbox-is-almost-full-in-outlook-365\/","title":{"rendered":"How to Fix Error \u201cYour Mailbox is Almost Full\u201d in Outlook 365?"},"content":{"rendered":"

Outlook 365 stores the mailbox data (emails, contacts, calendars, tasks, journals, notes etc.) in the OST file, which has a limit of 50 GB. However, Outlook users start experiencing issues when the OST file grows large and exceeds 10 GB size. These include send\/receive errors, slow search results, slow Outlook load time, etc.<\/p>

When the OST becomes too large and reaches the limit (10 GB, 20 GB or more) set by the administrator, Outlook users start receiving the warning message “your mailbox is almost full.<\/strong>” This is a concerning message that must be fixed to ensure uninterrupted email services and avoid issues, such as Outlook cannot send or receive new messages<\/strong>.<\/p>

Luckily, there are various ways to overcome the issue of OST file storage space. The most known are the deletion of unwanted messages, clearing junk folders, disabling Cached Exchange Mode<\/a>, and many others.<\/p>

What Triggers the Outlook 365 Mailbox Full Error?<\/strong><\/h2>

Every day hundreds of emails are sent and received by Outlook 365 users, resulting in a shrinking of storage space. In addition to emails, large attachment files are also one of the reasons for receiving the mailbox full error. Therefore, it’s important for you to organize your mailbox in an efficient way to have decent storage space for your Outlook 365 profile.<\/p>

Below are the main reasons for receiving Outlook 365 mailbox is almost full error:<\/p>

1. Large Size of OST File<\/strong><\/h3>

The large size of Outlook OST<\/a> file is one of the reasons for Outlook 365 performance issues. Each Outlook profile is usually given a storage space of up to 50 GB (more in some exceptional cases). When it gets exhausted, the message of a mailbox full error occurs.<\/p>

2. Deleted Emails<\/strong><\/h3>

Most of the time, when a user gets irrelevant emails in the inbox, they delete them from the account not noticing the fact they’re going to the deleted items folder. They consume a large storage space resulting in receiving Outlook 365 mailbox full error<\/strong>.
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\"Deleted<\/figure>

Solutions to Fix Error “Your Mailbox is Almost Full” in Outlook 365<\/strong><\/h2>

Now, let’s learn the possible ways to fix the mailbox full error.<\/p>

Solution 1: Archive Mailbox Items<\/strong><\/h3>

To manage the Outlook 365 storage space, you can archive the older emails. Find the steps below:<\/p>

    \n
  1. Open Outlook and go to the File tab.<\/li>\n\n\n\n
  2. Select Info<\/strong> > Cleanup Tools<\/strong> > Archive.<\/strong><\/li>\n\n\n\n
  3. Check the Archive settings and select Archive this folder and all subfolders<\/strong> option.<\/li>\n\n\n\n
  4. Choose the mailbox items you want to archive from your Outlook profile.<\/li>\n\n\n\n
  5. Select the date when you want to archive the older items.<\/li>\n\n\n\n
  6. Click Browse to choose a save location.<\/li>\n\n\n\n
  7. Make sure to mark the “Do not auto-archive<\/strong>” checkbox.<\/li>\n\n\n\n
  8. Hit the OK<\/strong> tab<\/li>\n<\/ol>

    Solution 2: Remove Oversized Email<\/strong><\/h3>

    The oversized emails and attachments exhaust the Outlook 365 mailbox storage space easily. You can remove the large mail items and attachments by following the given steps:<\/p>

      \n
    1. Start Outlook 365 and select Search Folders in the folder pane.<\/li>\n\n\n\n
    2. Click on the New Search Folder<\/strong> and select Large Mail<\/strong> option under the Organizing Mail.<\/strong><\/li>\n\n\n\n
    3. Select mail at least this large and specify the mail size.<\/li>\n\n\n\n
    4. Press OK<\/strong> to finish.<\/li>\n\n\n\n
    5. A new folder of specified size will be created under your Outlook 365 profile. It contains mails larger than specified size automatically.<\/li>\n<\/ol>

      Solution 3: Use Outlook Clean Up Tool<\/strong><\/h3>

      Make use of Outlook cleaning tool to clear unwanted mails and attachment files from your mailbox. Follow the given steps:<\/p>