Why is my HTML email all messed up?

I've seen this crop up on occasion too and it's darn frustrating. From experimentation, it appears that there are two basic ways that an email message indicates that it's written in HTML format, and both revolve around something called the Multipurpose Internet Mail Extensions, MIME.

In the simplest case, the message is sent purely as HTML and there's an additional header added to the message that's Content-type: text/html. Omit that, or have it munged in transit and the nicely designed HTML message ends up being complete gobbledygook, as you see. Some tools at least add a line or two that's hidden when rendered in HTML but visible otherwise that says something like "You need an HTML capable viewer to read this message. If you're seeing this, you need to upgrade, or you can go to

The other, more complex, way to send an HTML message is to actually send multiple versions of the message, one that's just plain text, and one that's a fully detailed HTML message. This is done through what's called a "multipart alternative" message and its headers are a bit more complex. Here's an example:

Content-Type: multipart/alternative;
	boundary="----=_NextPart_000_001B_01C52196.92F3CF30"
X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0)
Importance: Normal

This is a multi-part message in MIME format.

------=_NextPart_000_001B_01C52196.92F3CF30
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 8bit

here's where the plain text part appears

------=_NextPart_000_001B_01C52196.92F3CF30
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

and this is the html part

------=_NextPart_000_001B_01C52196.92F3CF30--

Basically, you're getting the HTML message, but your mail program just isn't recognizing it as being formatted in one of these two ways (probably the former, I'm guessing).

The fix? If you can edit the message headers (In Microsoft Entourage, you can only edit the body, for example) then just add in the header Content-type: text/html. If not, you could try saving it as a ".html" file then opening it in Safari, Firefox or your favorite browser.

Either way, that's a pain and it'd be easier to communicate with the sender to find out why their mail program isn't creating proper and valid headers.