We created this for our usage, but decided it could be useful for other people too :) It's still under development, so there are not many features yet, but we would like to hear your opinions and what could we improve or add. Thanks!
One very useful feature would be to add up to date filtering systems in report only mode (eg SpamAssassin), SPF / DKIM / DMARC checks, etc. Without having your own up to date inbound MTA, it's very difficult to test your own mails for things that might be triggering spam filters.