You see an error stating the message size exceeds your sending limit when trying to send an email in Outlook. This error occurs because your email account has a maximum size limit for outgoing messages. This article explains the technical limits and provides steps to reduce your email’s size so it can be sent.
Key Takeaways: Fixing the Message Size Limit Error
- File > Info > Cleanup Tools > Mailbox Cleanup: Use this tool to find and delete large items from your mailbox to stay under server limits.
- File > Options > Mail > Empty Deleted Items folder: Configuring this setting helps manage overall mailbox size, which can affect sending limits.
- OneDrive or SharePoint link sharing: Attach large files via cloud storage links instead of embedding them directly in the email.
Understanding Email Size Limits in Outlook
The sending limit error is enforced by your email service provider, not by Outlook itself. Microsoft 365, Exchange Server, and other services like Gmail set a maximum size for any single outgoing message. This limit typically includes the email body, all attachments, and any embedded images. The total size of your composed message has surpassed this configured threshold. Common limits are 20 MB for older Exchange setups or 150 MB for modern Microsoft 365 accounts, but you must check with your administrator for the exact number. Exceeding this limit prevents the email server from accepting and routing your message.
Steps to Reduce Your Email Size and Send It
Follow these steps to make your email smaller and bypass the sending limit error.
- Remove or compress large attachments
Open your unsent message draft. Review the Attached line below the subject. Right-click any large file and select Remove. For necessary files, use a compression tool like ZIP before attaching the compressed archive. - Use cloud links instead of attachments
Save your large files to OneDrive, SharePoint, or another cloud service. In your Outlook email, go to the Insert tab and select Attach File. Choose Browse Cloud Locations and select your file. Use the Attach as a Cloud File option to insert a shareable link instead of the full file. - Compress images within the email body
If your email contains pasted images, click on one image. The Picture Format tab will appear. Select Compress Pictures. In the dialog box, choose E-mail (96 ppi) as the target output and apply to all pictures in the document. Click OK. - Check the MailTip for your limit
With the message open, look for a yellow MailTip bar below the ribbon. It often states the exact size limit for your account. Use this as a guide while removing content. - Save the message as a draft and restart Outlook
Close the message and save it when prompted. Exit Outlook completely from the system tray. Restart the application and reopen the draft. The size calculation may refresh, allowing you to send it if you already removed items.
Common Mistakes and Things to Avoid
Assuming All Attachments Are Visible
You might have hidden attachments like full-resolution images copied from a website or a large signature file. Check the message size by looking at the status bar at the bottom-right of the message window. It shows the total size. If it’s large with few visible attachments, review the email body for embedded objects.
Forwarding a Message Without Cleaning It First
Forwarding a long email thread with its own history of attachments can instantly exceed the limit. Instead of forwarding, create a new message. Summarize the content and attach only the specific files needed from the original chain.
Ignoring Mailbox Size Quotas
A nearly full mailbox can sometimes interfere with sending large messages. Go to File > Info and check your mailbox size. Use the Mailbox Cleanup tool to find and archive old items with large attachments to free up space.
Attachment Methods: Direct vs Cloud Link
| Item | Direct Attachment | Cloud Storage Link |
|---|---|---|
| Impact on Message Size | Increases total size by full file weight | Adds only a few kilobytes for the URL |
| Recipient Action to View | Open or download from email directly | Click link to view in browser or download |
| Best For | Small, final documents under 5 MB | Large files, collaborative drafts, or videos |
| Size Limit Constraint | Bound by your email server sending limit | Bound by your cloud storage share limits |
| Version Control | File is static snapshot when sent | You can update file in cloud after sending |
You can now identify and resolve the message size limit error in Outlook. Use the Mailbox Cleanup tool regularly to manage your stored data. For sending very large files, practice using the Attach as a Cloud File option from the Insert tab. A useful advanced tip is to hold the Ctrl key while clicking on multiple large emails in your Sent Items folder, then press Delete to quickly remove them and free up your sending quota.