How to Perfom SMTP Test Command in Linux

Q. I just installed postfix on my linux virtual private server (VPS), but i am not sure how to verify the SMTP service and perform SMTP test to ensure the email delivery working fine or not ?

A. In Linux, you can send email, peform SMTP test and diagnose email errors through the TELNET linux command :

As an example :

[root@localhost ~]# telnet localhost 25
Trying ::1...
Connected to localhost.
Escape character is '^]'.
220 localhost.localdomain ESMTP Postfix
helo abc.com
250 localhost.localdomain
mail from:user@scriptsmy.com
250 2.1.0 Ok
rcpt to:ehowstufff@gmail.com
250 2.1.5 Ok
data
354 End data with .
Subject: test Email From Scriptsmy.com
Hi,

This is just test email.

regards,
.
250 2.0.0 Ok: queued as A0E013CC6
quit
221 2.0.0 Bye

Type command 1 to command 7
Command 1 :

[root@localhost ~]# telnet localhost 25

Command 2 :

helo abc.com

Command 3 :

mail from:user@scriptsmy.com

Command 4 :

rcpt to:ehowstufff@gmail.com

Command 5 :

data

Command 6 :

Subject: test Email From Scriptsmy.com
Hi,

This is just test email.

regards,
.

Command 7 :

quit

Check the status in maillog

[root@localhost ~]# tail -f /var/log/maillog

Oct 18 06:01:49 localhost postfix/cleanup[20296]: A0E013CC6: message-id=<20141018060058.A0E013CC6@localhost.localdomain>
Oct 18 06:01:49 localhost postfix/qmgr[20267]: A0E013CC6: from=, size=401, nrcpt=1 (queue active)
Oct 18 06:01:50 localhost postfix/smtp[20318]: A0E013CC6: to=, relay=gmail-smtp-in.l.google.com[2607:f8b0:4003:c05::1a]:25, delay=76, delays=75/0.01/0.12/1.3, dsn=2.0.0, status=sent (250 2.0.0 OK 1413612110 yv8si3312807oeb.10 - gsmtp)
Oct 18 06:01:50 localhost postfix/qmgr[20267]: A0E013CC6: removed
Oct 18 06:01:53 localhost postfix/smtpd[20293]: disconnect from localhost[::1]