I first used rss2email[1], moved on to writing my own initially as a WP plugin (using the blogroll links to pull from); it gradually evolved into a standalone python thing to support mf2[2] feeds.

I do prefer RSS entries as email entries, therefore newletters and RSS feeds are more or less the same to me.

[1]: http://www.allthingsrss.com/rss2email/ [2]: http://microformats.org/wiki/h-feed