; the MX example says digitalocean.com, but substitute it with smtp device's FQDN
; yes, you can use the same FQDN for incoming and outgoing email
; a PTR record is not needed as long as the IP specified in the SPF matches
; the first column establishes priority, the third specifies type. Always end domains with a period in a Zone Editor when dealing with A, MX, NS or PTR records.
0   IN  MX  mx.digitalocean.com.