I use Google Apps for internal email. We use the Postini add on for archiving and spam filtering. I'm very happy with this set up. For sending newsletters, I u

I use Google Apps for internal email. We use the Postini add on for archiving and spam filtering. I'm very happy with this set up. For sending newsletters, I use Constant Contact. I previously used Campaign Monitor their per-email pricing model became far too expensive over time. Campaign Monitor's service really was excellent and I think I'll switch back to them now that their pricing has changed. (Wrote a blog post about the pricing policies of these services http://www.smithshop.com/price-convergence-and-mailing-list-services http://www.smithshop.com/price-convergence-and-mailing-list-...). For our transactional emails, we use PostmarkApp. Delivery wise--they are fine. Their admin interface leaves much to be desired. Searching old emails usually causes an application error. This bug (in a common functional area) has been happening for the whole time (1+ year) I've been using the service. Hopefully they'll spend some time and polish up the app a bit. I initially chose them over SendGrid because their pricing was better (at our levels) but I may switch over in the future. I've definitely chosen the SaaS/managed solutions over the 'roll-your-own' own email server. There are just too many (different kinds of) headaches involved with each of these not to outsource.