Message Size Limit Exceeded? Here’s What to Do Now
Why You See a Message Size Limit Exceeded Error
It’s 4:55 on the Friday before a long weekend. Your client presentation is finally done, you click Send, and Outlook fires back: “The file you’re attaching is bigger than the server allows.” A message size limit exceeded error is one of the most common email problems we fix for clients. Fortunately, the solution usually takes less than a minute once you know where to look.
The 1-Minute Summary
- Most email services cap a whole message at 20 to 25 MB, and your recipient’s limit is the one that counts.
- Attachments grow about 33% when they’re sent, so a 19 MB file can arrive as roughly 25 MB.
- Microsoft 365 allows 35 MB per message by default. Admins can raise it to 150 MB, but that won’t help when you send to Gmail or Yahoo.
- The fastest fix is to share a OneDrive or SharePoint link instead of attaching the file.
- For client documents, a link is also more secure, because you can set an expiration date and remove access later.
Common Message Size Limit Exceeded Error Messages
The wording changes depending on your email app and the recipient’s server. However, all of these mean the same thing: the message is too large to send or too large to receive.
- “The file you’re attaching is bigger than the server allows.”
- “Your message is too large to send. To send it, make the message smaller, for example, by removing attachments.”
- “550 5.2.3 message too large for this recipient”
- “550 5.2.3 RESOLVER.RST.RecipSizeLimit; message too large for this recipient”
- “The system is undeliverable, and the message size exceeds the outgoing message size limit.”
- “Unable to send email: Message size exceeds server limit”
- “Mail Delivery Failed: message size exceeds fixed maximum size”
- “552 5.3.4 Message size exceeds fixed maximum message size”
- “The size of the message you are trying to send exceeds the server’s global size limit. The message was not sent; reduce the message size and try again.”
- “Attachment size exceeds the allowable limit.”
Notice that some bounces arrive minutes after you click Send. In that case, your server accepted the email, but the recipient’s server rejected it.
Why a 20 MB File Becomes a 27 MB Email
Here’s the part that surprises most people. Email was designed for text, so every attachment gets converted into text before it travels. That conversion adds about 33% to the file size, as Microsoft explains in its Exchange Online limits.
As a result, a 20 MB PDF ends up being roughly 27 MB on the way out. That is over the 25 MB ceiling most providers use. So you get a message size limit exceeded bounce, even though the file looked small enough on your desktop.
Email Attachment Size Limits by Provider (2026)
| Email service | Typical limit per message |
|---|---|
| Microsoft 365 (business) | 35 MB send, 36 MB receive by default; adjustable up to 150 MB |
| Outlook.com (personal) | 20 MB |
| Gmail | 25 MB to send, 50 MB to receive |
| Yahoo Mail | 25 MB |
| iCloud Mail | 20 MB |
The lowest limit in the chain always wins, and that’s where most message-size-limit-exceeded bounces come from. If you send a 30 MB message from Microsoft 365 to a Gmail user, Gmail can still accept it. But send the same message to an iCloud or Outlook.com address, and it bounces.
5 Ways to Send Large Files When Email Is Too Large to Send
Each of these fixes a “message size limit exceeded” error within a few minutes, without waiting on IT.
1. Share a OneDrive Link Instead of Attaching
This is our first recommendation for every client. In Outlook, click Attach, choose the file from OneDrive, and select Share link. Your recipient gets a clickable link instead of a heavy attachment. Microsoft allows OneDrive file attachments up to 2 GB, far beyond any email limit.
2. Use SharePoint for Ongoing Client Projects
If you trade files with the same client every week, create a shared SharePoint folder. Everyone works from the latest version, and nothing bounces. We explain the bigger picture in Stop Replacing Servers You Don’t Need.
3. Shrink PDFs and Images
Large PDFs are usually full of high-resolution scans. In Adobe Acrobat, use the Compress PDF tool. In PowerPoint or Word, go to File > Compress Pictures. Either way, you can often cut the size in half without anyone noticing a difference.
4. Zip a Folder of Many Small Files
Right-click the files, then choose Compress to ZIP file. This works well for a batch of spreadsheets or text files. On the other hand, zipping files that are already compressed, like PDFs, JPGs, and modern Office files, saves very little.
5. Split It Across Several Emails
This is the last resort. It works, but it’s easy for your recipient to miss part 3 of 4. Use a link whenever you can.
What About Dropbox, Google Drive and WeTransfer?
They work, but there’s a catch for professional firms. When an employee uploads client files to a personal Dropbox or Google Drive account, those files are no longer under your company’s control. If that person leaves, so does your access.
You already pay for OneDrive and SharePoint with Microsoft 365. Our cloud services team can set them up so sharing is simple, secure, and logged. For more on protecting what leaves your inbox, read Outbound Email Security: Two Layers of Protection for Client Data.
Should You Raise the Message Size Limit in Microsoft 365?
Sometimes, but raising it rarely ends the “message size limit exceeded” errors. Raising your limit to 150 MB only applies to email between people within your organization. Once a message leaves Microsoft’s network, the recipient’s lower limit still applies.
Big attachments also fill mailboxes quickly. If your team keeps hitting storage warnings, see Microsoft 365 Mailbox Full? Here’s the Fix. In most cases, the better answer is a quick lesson on sharing links, not a bigger pipe.
Make Large File Sharing Easy for Your Team
A “message size limit exceeded” error is a minor annoyance. However, the workarounds people invent at 4:55 on a Friday, like personal file-sharing accounts, can create real security gaps.
Slingshot sets up secure OneDrive and SharePoint sharing for professional services firms across the North Shore, with expiration dates, access controls, and training your team will actually use. Book a free 15-minute strategy call, and we’ll show you how it works with your own files. Already a client? Contact our help desk, and we’ll walk you through it.
Frequently Asked Questions
What does “message size limit exceeded” mean?
It means your email, including its attachments, is larger than your server or the recipient’s server will accept. The message isn’t delivered until you make it smaller or send a link instead.
What is the maximum attachment size in Outlook?
For Microsoft 365 business accounts, the default limit is 35 MB per message, and admins can raise it to 150 MB. Personal Outlook.com accounts are limited to 20 MB. Keep in mind that the recipient’s limit may be lower.
Why did my email bounce when the file was under 25 MB?
Attachments grow about 33% when they’re encoded for email. A 20 MB file expands to about 27 MB, exceeding the 25 MB limit used by Gmail, Yahoo, and many others.
How do I send a file larger than 25 MB?
Share it as a OneDrive or SharePoint link. In Outlook, attach the file from OneDrive and choose Share link. Your recipient can then open or download it, and you avoid size limits entirely.
Is it safe to send client documents with a OneDrive link?
Yes, when it’s set up correctly. You can limit a link to specific people, set an expiration date, and remove access at any time. That’s more control than you have once an attachment lands in someone else’s inbox.
