Email is an essential form of communication in the modern world, and an email client (a program you use to read and write email) happens to be one of the few applications today that you can pretty much guarantee will allow you to communicate your ideas in a platform independant way - that is, if you send from your application, you expect that the person you sent the mail to can read your mail as you intended, even if they are on Windows, a Mac, Linux or some other operating system.
At least, that was the way the world was moving. Until Outlook 2007.
I use OS X Leopard in a business environment. And I choose to use Apple’s Mail client (called simply “Mail“). To be honest, Mail in Tiger (the previous version of OS X) was good, but lacked a lot of the integration that existed in something like Outlook 2003. With Leopard, it appears that while Apple was leap-frogging Outlook, Microsoft were moving Outlook backwards so that Apple didn’t need to jump so far. Apple produced a superior product. Microsoft produced a product setting email clients back years.
HTML Mail
There is this thing called standards. And there is also this thing called “modern” standards. Apparently, when Microsoft produced Outlook 2007, they decided to use Word’s HTML renderer rather than Internet Explorer’s (not that Internet Explorer is known for being overly standard compliant). The Word HTML renderer is years old, and does not follow modern standards. What this means is that Outlook 2007 users now have a mail client which incorrectly renders HTML mail.
I’m not a believer in sending HTML mail for all mail - I send most of my emails in plain text. But there is a time and place for everything. Sometimes you might want to send out an email that looks a little nicer - it could be some photos you want to show off, a business letter with a particular logo for a special purpose, or maybe just an invitation to clients that you wanted to impress.
And it is with the latter where I encountered my first Outlook 2007 problems.
After sending out an invitation from my company, a colleague came to me and told me that he couldn’t read the text in the mail. Apparently it was all black. I pointed out I had sent standard HTML, and asked what client he was using. It was Outlook 2007.
Everyone else could view the mail - though most were using OS X Leopard, so that wasn’t surprising. However, one person was using Outlook 2003, and it rendered fine. Another was using Thunderbird. So I needed to do some research, and discovered the Outlook 2007 HTML rendering problem.
To see how much of a problem this is I created some HTML mail and sent it to a friend. It was a complex looking mail that uses Leopard Mail’s stationery (and was trivial to create I might add). It included fancy photos, background images, and a central text area for the body of the mail. Here is the mail as it appears in Mail (click to enlarge).

HTML Mail in Apple Mail
As you can see, the mail looks pretty good - it is clear, it is artistic, it is creative. But I stress - it’s standard HTML. Any modern browser can view that HTML. There is nothing “Mac specific” - whatever that means.
Now, let’s compare this to how this mail looks in Thunderbird and Outlook 2003 (click to enlarge).
Thunderbird HTML Mail
Outlook 2003 HTML Mail
That looks pretty good - they both did a great job. Now lets compare with Outlook 2007 (Click to enlarge).

HTML Mail in Outlook 2007
That’s a complete balls up. Imagine if the background had been dark - you wouldn’t even see the body text. That was what happened with the invite I mentioned earlier.
And the most amazing thing is that the older version of Outlook rendered the mail correctly!
Inline Images
Ok, so Outlook 2007 is bad with HTML. What about general mail you’d send in a business environment?
Recently I sent some mail to another company. It was a bug report - straight text, with some inline images pointing out the problems I’d found. The people I’ve worked with have been doing this for years - text mail with inline images is an essential part of doing business over email.
Here’s an example of me sending some mail with inline images. First, on Leopard’s Mail (click to enlarge):

Text Mail with Images in Apple Mail
As you’d expect, Thunderbird and Outlook 2003 can render this mail correctly. Certainly Apple Mail handles inline images a little better by making them look like part of the mail, but it is still very readable and easy to access.
Thunderbird Text Mail
Outlook 2003 Text Mail
What about Outlook 2007? Surely Microsoft couldn’t get this wrong?
Well apparently, yes they can.

Text Mail with Images in Outlook 2007
Mail sends the mail as multipart mime. That’s to be expected. Alternating text and images.
Outlook 2007 takes the first bit of text, puts that as the body, and then adds as attachments each image, and each following piece of text between images as a separate attachment. Basically, the mail is unreadable - you have to pull out each of those ATT*.txt files. As you might have guessed, the person I sent the original mail to asked me to send them something they could easily read.
Conclusions
At best, Microsoft look to be incompetent - surely they test their email client with other email clients? At worst, Microsoft have purposely crippled their email client, ensuring people don’t switch to an alternative email client as they can’t be sure email will look the same when it reaches those using Outlook 2007.
What can you do here? Well, you could avoid Outlook 2007 until Microsoft fix it. If you are the administrator of Windows machines at your company, don’t let your staff upgrade. Move them to Thunderbird perhaps.
If you really must send Outlook 2007 friendly mail, your best bet is to convert your message to PDF, and send the PDF. Not exactly convenient I know.
But I personally think we should send out even more HTML mail. If Microsoft don’t want to follow standards, make them follow standards. If you are on a Mac, send lots of stationery based mail to your friends. If they tell you they can’t read it, tell them it is Outlook 2007, and if they want to participate in the modern world of email, they’ll need to use a modern email client. Microsoft don’t have the power they once had, regardless of their market share. It’s a brave new world.