Is there a limit on the size of individual email messages?

This page is showing a generic answer.

Our email servers allow incoming and outgoing messages up to 40 MB in size, including any attachments. However, there are other limitations that make it a good idea to keep them below 15 MB.

On this page:

You should probably make sure your email message attachments are less than 15 MB. That’s because any message you send goes through both our mail servers and the recipient’s mail servers, and it’s common for other mail servers to reject any message larger than 15 MB.

For example, if you send a 30 MB message to a Gmail, Comcast or Yahoo email address, our email servers will accept the message from your mail program, then try to deliver the message to the other company. However, the mail servers at Gmail, Comcast or Yahoo will reject it because it’s too large, and it will be returned to you as "undeliverable".

Note that 15 MB is just a recommendation. Some people you write to may be using mail servers with even smaller limits.

Encoded attachments are larger than you think

If you’re familiar with other mail services, you might know that many of them claim to accept messages up to 25 MB. If so, you’re probably wondering why we suggested "15 MB" above.

Here’s why: when you send a message with attachments, your mail program usually converts the attachments with "Base64 encoding" so they can be safely sent through email. However, this has the effect of making them 33% larger than their original size: for example, a 15 MB file is actually almost 20 MB when encoded.

Although a 25 MB limit is a common number, some large companies, including Time Warner Cable, reject any mail that’s over 20 MB. Keeping the size of any attachments below 15 MB makes sure that the actual message the other ISP receives is smaller than 20 MB.

Can Tiger Technologies increase the limits for me?

We unfortunately can’t increase the limits, for two reasons.

The first is that as long as our limits are higher than the limits of other popular companies (which they are), there’s no point to increasing them. Doing so wastes your time and network resources by allowing you to upload large attachments (which can take several minutes), then returning them undelivered when the other companies reject them for size reasons. It's better to see an error message about the size as soon as you start sending.

The second is that the software we use to run our mail servers, especially the spam and virus filtering software, has limits on how quickly it can process data. Limiting the size ensures our mail system runs at the near-instant speeds needed to handle email. (This is the primary reason that every company has limits on the size of messages.)


Our Webmail system has the same 40 MB size limit as any other mail program.

However, uploading large attachments with Webmail on a slow connection can take a while, which may cause problems in some Web browsers such as "timeout" errors. (This problem is a limitation of all Webmail systems, not just ours.)

Sending too-large attachments in Webmail can show an error saying either that the files are too large, or occasionally this more obscure message:

Email delivery error
Server replied: 75 Can't execute command /usr/sbin/sendmail 

If you have timeout problems or see these errors sending large attachments with Webmail, we strongly recommend using a mail program on your own computer, such as Outlook or Thunderbird.

Sending files by email has other potential problems

In addition to the size problems, keep in mind that many businesses (and even some ISPs) now reject different kinds of attachments in an effort to stop viruses. For example, some businesses simply reject all .zip files.

How to avoid the problem

Some mail programs, including Apple Mail, have a feature that automatically uploads any large attachments to a temporary website from which the recipient can download it.

You can do the same thing manually by putting the large file on your own website (or on a file sharing service like DropBox or Google Drive), then sending the recipient a link to the file instead of the file itself.

As an example, if you wanted to share a file named, simply upload it to your website, then send the recipients a normal text email message telling them to click on this link:

When a recipient clicks it, the file will download in his or her Web browser.

Nobody else will be able to download the file unless they know the exact file name. For added security, you could name the file something more obscure, like, and make the link:

If the file contents are important and you need even more security, you may wish to put the file in a protected directory.