Jun 102011
 

Normally, to check if my server smtp connection alive, I just do telnet to port 25 from my workstation. if the smtp banner displayed, it means that the connection to the smtp server is good. I have done this for years.  😆

$ telnet smtp.example.com 25
Trying xxx.xxx.xx.xxx...
Connected to xxx.xxx.xx.x.
Escape character is '^]'.
220 smtp.example.com ESMTP Postfix
ehlo host.example.com
250-smtp.example.com
250-PIPELINING
250-SIZE 52428800
250-ETRN
250-STARTTLS
250-AUTH LOGIN PLAIN
250-AUTH=LOGIN PLAIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
quit
221 2.0.0 Bye
Connection closed by foreign host.

Although many tools that are deliberately created for this purpose, still, I prefer just using telnet to port 25. I have made a simple perl script, with the intention that the things I do for years manually can be done automatically.

Modules required:

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Sep 092009
 

Extended SMTP

Extended SMTP (ESMTP), sometimes referred to as Enhanced SMTP,is a definition of protocol extensions to the Simple Mail Transfer Protocol standard.
The extension format was defined in IETF publication RFC 1869 (1995) which established a general structure for all existing and future extensions.
ESMTP defines consistent and manageable means by which ESMTP clients and servers can be identified and servers can indicate supported extensions.

Extensions

The main identification feature is for ESMTP clients to open a transmission with the command EHLO (Extended HELLO), rather than HELO.

Some relatively common keywords (not all of them corresponding to commands) used today are:
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