Buttondown

Buttondown is presented as a small, elegant tool for producing newsletters, from the company of the same name in Seattle. The minimalist interface enables users to focus on writing emails; the automation acts like an editorial assistant by checking for typos, broken links, or malformed images; the portable subscription widget makes it easier to grow an audience from wherever a site is hosted.

The vendor states Buttondown's focus is on pragmatism over richness; it's not the most robust application, but it may be the right tool where simple, low cost tool is preferred.