During a setup change I had to temporarily move my incoming mailserver to Gmail and while I am now back in my own mail server, I again had this major headache of configuring the my DNS (using BIND) because I always forget the dots in the end of CNAME and MX records because usually I dont create nameserver records for external domains… So anyway here is the final configuration I used in Hetzners Domain Robot:

mail                     IN CNAME   ghs.google.com.
@                        IN MX 1    ASPMX.L.GOOGLE.COM.
@                        IN MX 5    ALT2.ASPMX.L.GOOGLE.COM.
@                        IN MX 5    ALT1.ASPMX.L.GOOGLE.COM.
@                        IN MX 10   ALT4.ASPMX.L.GOOGLE.COM.
@                        IN MX 10   ALT3.ASPMX.L.GOOGLE.COM.