"Normal" users (i.e. the non-geeks) do seem to prefer HTML emails, and in usability studies, A/B testing, and deliverability reports, HTML emails usually outperform text.
In short, HTML emails are better for and preferred by recipients and senders in all but edge cases.
I have dealt with quite a bit of clients and they love to use colors as separation for various degree and scaffolds of conversations.
For now, if I'm initiating an email and do not really need to be HTML, I try to stay with text. For other, I just follow the format the current email thread is in.
If your goal is to distract and confuse people, by getting them to click on your ads and buy your products, then use HTML e-mail. If you want to communicate clearly, then stop worrying about layout & typography and concentrate on the words you are writing.
For me, it's all about keeping some control over technology. I tell a very limited program like mutt what to do, and it does it. This is in contrast to begging an incredibly complicated program like a browser to do something, where much of what it is doing is controlled by invisible embedded code written by people who may be hostile toward me.
Also, text-only doesn't mean monospace. I'm happy to read email in whatever sans-serif font the email client picks, with nice whitespacing.
> We began by asking, what layouts work well on mobile? The answer for us was to think “single column.”
This is nearly always the case. You can include pictures, and then use `align="right"` (or left) to make text float round the picture. You can use media queries to hide the picture entirely on mobile.
You can also use two buttons, one for mobile (which stretches to 100% width and more height) and one for desktop.
We use Litmus (http://litmus.com) to render test everything.
I have a strange love for coding HTML emails, so if I can help anyone with a bit of free advice, feel free to ask. @blowski
One of the bests to my knowledge is by Zurb [1], but the lack for Outlook support makes it almost unusable (at least for us). We ended up hacking from "the bigs" (Twitter, Facebook, Linkedin), although at the very beginning their templates also had issues here and there.
This said, testing on so many devices is a pain... email services like Mailchimp or Mailup should definitely add tools for that! (anyone listening? ;)
For general information, Anna Yeaman over at STYLECampaign made an amazing video on Responsive Email Design, a must-view if you're interested in the topic - http://stylecampaign.com/blog/2013/03/responsive-email-desig...
Shameless self promotion, I also wrote a book on the subject called Modern HTML Email - http://modernhtmlemail.com - good way to get into responsive email design and email marketing in general.
I think most ESPs do these days.
Another challenge on mobile is that most of the times images/ background-images aren't served at all. So as long as there is just text and style on your email this strategy would just work. The moment you decide to step-up the visuals, you'd start thinking why the hell does the world still use email at all?
That said, some folks go with image-heavy emails to encourage people to turn on the images. ASOS are particularly well known for this.
And if you want to get really creative when dealing with image-blocking - http://www.campaignmonitor.com/blog/post/3642/email-with-pix...
I wish all email clients behaved properly and used their browser counterpart's engine.
Meaning, Outlook would use IE9 or 10 render engine, et al.
