smtp-cli — command line SMTP client

smtp-cli is a powerful SMTP command line client with a support for advanced features, such as STARTTLS, SMTP-AUTH, or IPv6 and with a scriptable message composition capabilities supporting anything from simple plain-text messages right up to building complex HTML emails with alternative plain-text part, attachments and inline images. The MIME-Type of the attachments can either be guessed automatically or alternatively set on the command line, separately for each attachment if required.

It's also a convenient tool for testing and debugging SMTP servers' setups. Even the hardcore mail admins used to typing the SMTP protocol over telnet need a specialised tool when it comes to verifying encryption settings of their TLS enabled server with a subsequent user authentication. Such things are pretty hard to type into a telnet session by hand :-)

The name smtp-cli stands for:

  1. smtp-client
  2. smtp-command line interface

Use the script for checking given server's capabilities, test you server's setup or create and send mails. Command line interface is intuitive, everything is scriptable and can run in a completely non-interactive mode from various scripts or cron jobs. It is also ideal for shipping log files from remote machines, running periodical mail delivery test loops, etc. Also if you ever needed to send a complex email with attachments from a command line, this script is all you need.

Download the latest version
Optional dependencies

Some features of smtp-cli are optional and available only when the appropriate perl modules are installed:

Users of other Linux distributions will have to find the appropriate packages by themselves, or install the modules directly from CPAN.

Make it executable
$ chmod +x smtp-cli
Test on your localhost:
$ ./smtp-cli --verbose --host=localhost
[220] ' ESMTP Postfix'
> EHLO localhost
[250] ''
[250] 'SIZE 20480000'
[250] 'ETRN'
[250] '8BITMIME'
[221] 'Bye'
Send an e-mail through a host which requires authentication after an encryption takes place:
 ./smtp-cli --verbose --enable-auth --user test \
--from --to --data message-body.txt
[220] ' ESMTP Postfix'
> EHLO localhost
[250] ''
[250] 'SIZE 10240000'
[250] 'VRFY'
[250] 'ETRN'
[250] 'STARTTLS'
[250] 'XVERP'
[250] '8BITMIME'
Starting TLS...
[220] 'Ready to start TLS'
Using cipher: EDH-RSA-DES-CBC3-SHA
Subject Name: /C=XX/
Issuer  Name: /C=XX/CN=Domain.TOP Root CA/
> EHLO localhost
[250] ''
[250] 'SIZE 10240000'
[250] 'VRFY'
[250] 'ETRN'
[250] 'XVERP'
[250] '8BITMIME'
[334] 'PDE0OTQyOTcxOC4yNjAwOTYwQHNlcnZlci5kb21haW4udG9wPg=='
> dGVzdCBmOTUyY2RkM2VlODBiMzk1YjYxNDI4NjBlYzg2Y2ExZnJvb3Q=
[235] 'Authentication successful'
Authentication of test@localhost succeeded
[250] 'Ok'
> RCPT TO: <>
[250] 'Ok'
[354] 'End data with <CR><LF>.<CR><LF>'
[250] 'Ok: queued as C5C3A299D7'
[221] 'Bye'
Compose a plain text email with attachments

For composing emails you're gonna need an optional MIME::Lite perl module. See the download section above for details.

./smtp-cli --from --to \
                 --subject "Simple test with attachments" \
		 --body-plain "Log files are attached." \
                 --attach /var/log/some.log@text/plain \
		 --attach /var/log/other.log

Pretty self-explanatory, isn't it? Standard plain text email with attachments. The only interesting bit is the syntax used for enforcing MIME-Type of the second attachment. The syntax some.log@text/plain will make some.log attached as text/plain part, while the MIME-Type of other.log will be guessed by the script and eventually default to application/octet-stream.

Attachment as an email body
./smtp-cli --from --to \
                 --subject "Image as a mail body" \
                 --attach /path/to/tux.png

If there is only one text or image file to be sent, the file itself could be the message body. At the same time it will be accessible as an attachment with a file name for easy saving. Best to show a screenshot I guess...

There is no Text or HTML body part and the email is not multipart/mixed. All that is in the email is Tux the Penguin image. You can immediately see it in your mailer but also can easily save it with its provided name tux.png. The same way it works with text files (or files forced to be text/plain, to be precise).

Compose a multipart/alternative email with both HTML and Plain text part and inline images

Sending HTML emails is popular, especially among non-technical people. They like to change font colours, backgrounds, embed images and apply all sorts of other useless effects to their one short line of text. Indeed, me and you are more than happy with plain text and we both know that some mail readers can't even display colours and graphics at all (our office manager wouldn't believe!). And therefore it is a good practice for HTML messages to use multipart/alternative MIME format with both HTML and TEXT parts. In this example we're going to go wild and even embed an inlined image or two into the HTML part.

However first of all prepare the message body. Or bodies, actually. First one is body.html:

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<body bgcolor="#ffffff" text="#000000">
<div align="center">
Here comes embedded <font color="#006600"><b>Mr Tux</b></font><br>
<img src="cid:tux.png"><br>
<i>Nice, isn't it?</i><br>
<img src="cid:smiley.png"><br>

Note the <img> tags with source — that's the way to refer inlined attachments from inside the message. We will obviously have to inline-attach tux.png and smiley.png to the message to make it work.

Anyway, the second body file is a plain text representation of the above, call it body.txt:

Here comes embedded Mr Tux
... actually it doesn't ... 
Not in a text-only mail reader.

That's it. Here comes the magic command line that puts it all together:

./smtp-cli --from --to \
                 --subject "HTML with embedded image" \
		 --body-html body.html --body-plain body.txt \
		 --attach-inline tux.png --attach-inline smiley.png

And this is what we get:

Screenshot of inlined images


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