I loathe HTML email for many reasons. Privacy and security are two. A Google search for "html email security" returned about 328,000,000 results and "html email privacy" returned about 2,010,000,000 results. That's billions, folks.
For me, it's one of those "just because you can doesn't mean you should" things. I just analyzed a corpus of 4267 messages, a mixture of personal and marketing, looking for image references. One message contained 343 references to images. Seriously? I have less images of my wedding, one of the most important events of my life. The size of the message, without the images downloaded - 188K. I don't have the time to download all the images and come up with a true size.
Since this is a mixture of personal and marketing messages, I assumed (wrongly I'm sure since this is just a quick analysis) that messages with 0 to 10 image references were personal. That eliminated 2940 messages. Of the remaining 1397 messages:
- 79 (about 5%) contained 100 or more image references
- 164 (about 12%) contained between 50 and 99 image references
- 1154 (about 83%) contained between 11 and 49 image references
The total image references for the entire corpus - 62,183. That's 62,183 DNS calls. That's 62,183 HTTP transactions. And it's email. See this interesting graphic about an HTTP call.
A recent study showed that mobile email viewing is rising and desktop and webmail viewing is declining. See http://www.returnpath.net/landing/emailonthemove/. So when I get close to my data allowance on my iPhone, the first thing to go will be the marketing messages I signed up for that don't offer a text version.