SWAKS: the SMTP Swiss Army Knife

flash_m_laser_1200_900
SWAKS is a general purpose testing tool for SMTP. For basic SMTP testing it’s a more convenient, scriptable alternative to running a transaction by hand, but it also lets you test things that are difficult to do manually, such as authentication or TLS encryption.
It’s a perl script that installs fairly easily on OS X or any Linux/unix system (and can be installed on Windows, if you have perl installed there).
It’s pretty well documented, but it can be a bit overwhelming to start with. Here are some simple recipes:
Send a test email:

swaks -f you@example.net -t someone@example.com

Check to see if a recipient exists:

swaks -f you@example.net -t someone@example.com \
        --quit-after RCPT

Send via a particular server:

swaks -f you@example.net -t someone@example.com \
        --server mail.example.com

Test user authentication for a smarthost:

swaks -tls --server example.com -f you@example.com \
        -t someone@example.net  -ao --auth-user=you

Test to see if a server supports opportunistic TLS:

swaks -tls -s mail.example.com -f you@example.net \
        --ehlo your.host.name --quit-after FROM

(The backslashes are just there to split a single command line into two, so you can read it easily on this narrow blog).
SWAKS has a lot of other tricks too – adding headers, using specific protocols and ports, attaching content. It’s a very useful tool, and gets even more so when you add a little bit of shell scripting to automate your testing further.

Related Posts

SMTP Level Rejections

While discussing a draft of a Deliverability BCP document the issue came up of what rejections at different phases of the email delivery transaction can mean. That’s quite a big subject, but here’s a quick cheat sheet.
At initial connection
Dropped or failed connection:

Read More

8 things that make your mail look like spam

In the comments of last week’s Wednesday question John B. asked

Read More

Troubleshooting tools

There have been a number of comments on my post about Hotmail moving to SPF authentication having to do with troubleshooting authentication failures. I have been helping clients troubleshoot these issues, and am able to take on new clients to solve authentication problems. Contact me for more information.
Of course, many of these issues can be solved with access to the right tools. Steve’s been working on a number of tools that may help the troubleshooting process and we’ve recently launched them on Emailstuff.org. The website itself contains a number of DNS and data related tools we use for investigations and thought we’d share with the public at large.
One of the really useful tools is the SPF record expander. Plug in any domain, like google.com, and see what IP addresses they authorize to send mail.

Read More