Change default Message size restriction in Outlook.

You can change the default for your organization by adjusting the default message size restriction. Simply select recipients > mailboxes then click “. . .” and select Set default message size restrictions.

You can then specify the maximum message size for new mailboxes (those you create in the future).

To edit multiple mailboxes select recipients > mailboxes and select multiple mailboxes. Then from the Bulk Edit pane under Message Size Restrictions select Update.

Finally, you can customize a single mailbox by selecting recipients > mailboxes and then select a user’s mailbox. Click the edit icon , then under Message Size Restrictions, click View details and then specify the maximum message size.