Magpie Tech Tips

November 01, 2013

Why Does My Company Limit Email Attachment Size?

It's 2013. Why do we still have a size limit on email attachments? Most offices still cap attachments at 10MB. There's a good reason for has to do with a mail server's functions. Read our Tech Tip for the explanation.
Are you stuck with a 10MB size limit on attachments for your work emails? There’s a reason for such a small size limit, but it might not be the one you think.

Most people think an attachment size limit is done to protect your network. If a hacker kept sending emails with huge files to your mail servers over and over, it would crash the server. They’re right, but there are even more legitimate reasons to limit email attachment sizes.

From a corporate standpoint the most common reason is that mail servers are not file servers, but users treat them as such. A mail server is built to send messages. Not to store files. That’s what a file server is for (e.g., Windows Server, SharePoint, Anchor). By sending big files via email, users can treat a mail server like a file server. Storing files in their email, where they shouldn’t be.

So it makes sense to keep a limit on email attachment sizes. If you have a big file you need to send to someone, put it on your company's file server. If you don't have a file server, here are a few online services which can send large files to other people for you. Note, we cannot guarantee the security of files transferred over these services: and

Another reason IT departments limit attachments to 10MB is because most other mail servers do. In other words, emails that are 10MB or larger that you send may be returned to you. A 7MB message after encoding will be 33% larger, and will exceed the 10MB limitation of most mail servers. Microsoft Exchange has a default limitation of 10MB. Comcast and EarthLink have 10MB limitations. Juno rejects mail over 5MB and NetZero rejects mail over 2MB. So even if your company allows larger email sizes your mail more than likely will be rejected if it is over 10MB.