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Updated on August 18, 2022

How to Restrict Message Size Limit in Microsoft Office365?

Setting A Limit For Message Size

Restricting message size limits is not bad as it sounds – it’s actually helpful in managing your mailboxes to make sure all email messages over the Internet go through smoothly.

Here is the rationale behind it:

  • Just as in transferring files from a computer to a drive, sending large files over email will take time. And if all messages contain huge chunks of attachments, servers would experience delay in sending messages to and from different email addresses.
  • Mailboxes have limited space allocated for each user. So, you want to make sure that you do not, and your users also do not, use up that space in a single email.
  • Assigning a message size limit is also a security measure. It’s a precaution to ensure that data such as program files cannot be easily sent over email.


Here’s how you can do it in Office365:


How To Restrict Message Size Limit In Office365?

  1. Log in to Office365.
  2. Go to Admin, and you should see the Exchange admin center.
  3. From here, click on recipients, then select mailboxes.

    Under Mailboxes, click on the dotted lines to display the menu and click on Set default message size restrictions.
  4. You can now set the default message size limit (in KB) for all incoming and outgoing messages. Once done, click on ok.

  5. Here’s how you can modify settings for multiple mailboxes:
    • Go to the Exchange Admin Center, then recipients and mailboxes.
    • Select multiple mailboxes.
    • Go to the Bulk Edit pane under Message Size Restrictions.
    • Then click on Update.

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