Review on DMARCLY by Aaron Bannister

The integration with multiple providers is great; it makes troubleshooting easy for any provider that we use across our domain(s). It's free for testing purposes but you will have to pay per month if you want hosting of your own data or plan for using their API. They do not support other services like Google Apps as well. I've been in contact with them via forums and they are very responsive. We needed an SMTP gateway option to solve sending issues at times when we were out of office hours or had technical problems at the time of sending emails. This solved those issues.