Depends what kind of security, availability is a part of it. When you forget your password (or it gets hacked and someone changes it), you can just re-deploy the whole thing. On Gmail you might be screwed. On self-deploy backups seem mandatory, which mail user backs up his or her E-Mails?

As far as I have heard, if SPF, DKIM etc etc is properly configured, blocking won't happen. I don't have this running yet but this is my next project. Probably I'll go with postfix, there are bizillion plugins for exactly these things and the configuration will be automated with Ansible. So once it's up and running, I expect this to be pretty much care-free.