Keep in mind that email programs handle things like pictures in various ways, especially inline vs. attachment. So whoever can help you with this probably wants to know the email program, and the blog (e.g. Blogger, WordPress, etc. or a master control like HootSuite.)
A few years ago I did some tests with Eudora and inline pics mailing to Blogger and Wordpress. I can look for a thread but could not check my results for a couple of days. I remember there was variation in picture sizing, although one blog worked well.
I was trying to do it without any conversion, with HTML conversion the target may not matter.