[root@development_techx ~]# hostname
development_techx
[root@development_techx ~]# grep -i techx /etc/hosts
127.0.0.1 techx.com
::1       Development_techx
127.0.0.1 autoreply.Development_techx
45.77.141.129     techx.com
127.0.0.1     localhost development_techx  techx.com Development_techx
#127.0.0.1     localhost localhost.localdomain  techx.com
45.77.141.129 techx.com
[root@development_techx ~]# grep hosts: /etc/nsswitch.conf
#hosts:     db files nisplus nis dns
hosts:      files dns myhostname
[root@development_techx ~]# cat /etc/mail/service.switch
cat: /etc/mail/service.switch: No such file or directory
[root@development_techx ~]# nslookup smtp.techx.com
Server:         108.61.10.10
Address:        108.61.10.10#53

** server can't find smtp.techx.com: NXDOMAIN

[root@development_techx ~]# nslookup techx.com
Server:         108.61.10.10
Address:        108.61.10.10#53

Non-authoritative answer:
Name:   techx.com
Address: 45.76.182.101

echo "hello" | mail mohtashim@techx.com

more test.sh
#!/bin/sh
TO=mohtashim@techx.com

# -i  - do not treat special lines starting with "."
# -v  - use verbose mode (provide SMTP session transcript)
# -Am - use sendmail.cf (do not send via localhost:25) - requires root privileges
/usr/sbin/sendmail -i -v -Am -- $TO <<END
Subject: Delivery test
To: $TO

Delivery test.
END