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Unable to send emails in Outlook

Sammy S 0 Reputation points
2025-08-07T21:50:30.9933333+00:00

Hi, I'm able to receive emails in Outlook but not send them. Every time I try to send an email, I get the message "Your message couldn't be delivered because it's too large. The limit is 1 KB. Your message is 7 KB." I'm using a Macbook Air. I can send emails through my gmail account for that account, but I can't send them through Outlook. I have tried resetting my account, I've only used 2gb out of 99gb of storage, I've updated my laptop, and I've logged in/out of my email multiple times. Nothing seems to work. I also tried switching from Legacy to the new version, I can't send emails in either version. It's an Office 365 account given to me through my college/work (I currently attend the university and I used to work for its hospital).

Outlook | MacOS | New Outlook for Mac | For education

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  1. Vergil-V 2,115 Reputation points Microsoft External Staff Moderator
    2025-08-08T01:50:40.0633333+00:00

    Hi @Sammy S 
    Thank you for reaching out to the Microsoft Q&A forum! 
    Based on your description, I understand you're encountering the error message "Your message couldn't be delivered because it's too large" when sending an email using Outlook for Mac. I understand how frustrating this issue can be, and I want to assure you that I’m here to support you as we work through it together 

    To better understand the scope of the problem, could you please confirm whether the same issue occurs when using Outlook on the Web (OWA)?   
    You can access OWA by visiting https://outlook.office.com/mail/ in any browser on your device. Try sending a test email and let us know if you receive a similar error message. 

    If the issue also occurs in OWA, it's quite likely that your school's IT team has configured a message size restriction on your mailbox. In my own testing, I received a similar error when message size limits were exceeded. Therefore, I strongly recommend reaching out to your IT department to verify the current message size limits applied to your account.  For reference, here’s a helpful article from Microsoft Learn: Configure message size limits for a mailbox | Microsoft Learn 

    Additionally, here’s an example of how to check the message size restriction for a specific mailbox in my test environment: 

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    If your IT team confirms that no size restrictions are configured for your mailbox and the issue still persists, please share the following details to help us investigate further: 

    Question 1: Could you please share the current configuration of your mailbox's message size restriction, along with the complete error message you received? 

    Question 2: Could you please confirm the version of Outlook for Mac you are currently using? Additionally, did this issue begin when you first started using Outlook for Mac, or did it occur after a recent update or a rollback to a previous version? 

    Before sharing, kindly ensure that any personal or sensitive information (such as your email address, organization domain name, etc.) is removed to protect your privacy and to ensure your reply is valid. 

    I sincerely hope this information partially clarifies your situation and assists you in planning your solution. Please do not hesitate to reply if you have any updates. 

    Thank you for your understanding. 

    If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". 

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread. 

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