I used to be a big fan of Mandrill. I used to use it as an email gateway for my personal servers. It’s easy to use and it’s cheap (Or free if you send less than 12,000 emails per month). I liked not having to setup SPF, DKIM, and DMARC for my small setups. Even for smaller clients I wouldn’t bother with that and just use Mandrill. Emails just show up with the following sender
Sometimes when you have a high number of outgoing messages services like Yahoo! and Gmail might block you. To prevent that you need to distribute your outgoing emails through a set of IPs. I used HAProxy for that along with a number of FreeBSD Jails. That solution is a bit tedious, even though after I started using Salt things became a bit easier it was still too complicated for my taste.
I’ve been busy setting up a PHPlist server for my employer. All tests went ok, but as soon as we sent our first newsletter Yahoo! blocked the server. After looking around for a solution people suggested we sign all outgoing emails with DomainKeys and not hammer Yahoo’s servers with consecutive connection.