[joshfraser]

I did some A/B testing on this a few years ago and found that HTML email had a better response rate for me. My methodology wasn't perfect, but I shared the results on my blog anyway: http://www.onlineaspect.com/2008/01/25/the-value-of-split-te...

[huhtenberg]

That was 4 years ago. Things change way too fast for your sampling to remain relevant for this long.

[adrianhoward]

It's been what I see in tests too. A well designed HTML mail will generally beat a plain text mail in response rates... including the one we did for $client last week ;)

[nihonjon]

troll elsewhere