Sendmail is not working and getting "connection refused" for 127.0.0.1.

Issue

• Getting following error in maillog for sendmail:

  Apr 23 14:14:49 hostname sm-msp-queue[13859]: t3LMF2ZO0069: to=localuser, ctladdr=root (0/513), delay=1+19:59:47, xdelay=00:00:00, mailer=relay, pri=3990502, relay=[127.0.0.1], dsn=4.0.0, stat=Deferred: [127.0.0.1]: No route to host
  

• Mails aren't working for local users also.