I needed a tool to check mail servers for open relaying and proper dns settings. There are several web sites providing such services, but I like my tools locally if possible.
As I couldn’t find such a tool, I wrote one. You can find it on Github:
https://github.com/steffenfritz/mxcheck
With golang installed you can go get it with
go get github.com/steffenfritz/mxcheck
Usage is simple:
./mxcheck -t TARGETHOST