I'm also using critsend. It works very well for both transactional and newsletters. All my transactional mail are initiated from ruby webapp processes. Crea

I'm also using critsend. It works very well for both transactional and newsletters. All my transactional mail are initiated from ruby webapp processes. Creating newsletters turned out to not be too much coding. I wrote a ruby lib for batch sending against a newsletter html which gets embedded into a well tested template. I write success and error info for the newsletter sends to a mongodb table. This is working well for me. Sending out a monthly newsletter to 20k subscribers takes about an hour to do a test send or two to verify I didn't screw up the html content and off it goes.