Use host
no Linux para mostrar todos os endereços IP relacionados a um nome de domínio.
sub@ubuntu:~$ host crashlytics.com
crashlytics.com has address 107.21.238.206
crashlytics.com has address 23.21.242.216
crashlytics.com has address 23.21.93.182
crashlytics.com mail is handled by 10 aspmx.l.google.com.
crashlytics.com mail is handled by 20 alt1.aspmx.l.google.com.
crashlytics.com mail is handled by 20 alt2.aspmx.l.google.com.
crashlytics.com mail is handled by 30 aspmx2.googlemail.com.
crashlytics.com mail is handled by 30 aspmx3.googlemail.com.
crashlytics.com mail is handled by 30 aspmx4.googlemail.com.
crashlytics.com mail is handled by 30 aspmx5.googlemail.com.