On my last assignment, we had a need for an occasional HTML email blast. I generally have relied on Mailchimp to make such emails but this was for a small, internal audience so such a service would have been overkill.
I did, however, use one of their templates to save some development time but still the execution was a little speculative.
I found this great post at CSS Tricks outlining a great workflow and suggested tools and wanted to share it.
Also, here is a valuable survey of some existing mail API’s you could use for your projects!