$ telnet mydomain.com 25
Trying <IP address removed>...
telnet: connect to address <IP address removed>: Operation timed out
telnet: Unable to connect to remote host

$ telnet localhost 25
Trying ::1...
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 hobnob Python SMTP proxy version 0.2

from smtplib import SMTP
conn = SMTP('mydomain.com')

dig +short mydomain.com MX