Friday 18 May 2012

Use telnet to test SMTP server

Besides testing HTTP server, telnet can also be used to test SMTP server

below is the testing I did on my linux box

$ telnet localhost 25
220 redhat.localdomain ESMTP Postfix
ehlo abc.com
250-redhat.localdomain
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
mail from: scripter@linux.com
250 2.1.0 OK
rcpt to: nonexsit
550 5.1.1 <nonexist>: Recipient address rejected: User unknown in local recipient table
rcpt to:tom
250 2.1.5 OK
data
354 End data with <CR><LF>.<CR><LF>
Subject: hi this is subject
this is email body

more chars
.
250 2.0.0 OK: queued as 25AE12AD1
quit
221 2.0.0 Bye

in /var/spool/mail/tom will see the email we just sent

please note the lines starting with numbers are the output returned by SMTP server, the numbers are the status code, search "smtp status code" for more details.
"ehlo", "mail from:", "rcpt to:", "data", "quit" are the commands sent to SMTP server.


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