I love the idea of abusing the fact that spammers are in a hurry. Traffic Control checks all the geeky check-boxes of a SMTP proxy I should take a closer look at.
So the first thing I do once I can netcat to the proxy and check it’s running is fire up a “tcpflow -c -i eth0 not port 22” to watch it in action. I could immediately see how it slows connections (sweet), and then the instant phone home traffic or feedback mechanism.
I’m not so sure I like the feedback mechanism. The main issue is “but not be limited to” statement in the license as usual not the fact that they aggregate logs, over http on port 25.

Exhibit #1 – License snippet :

17.Feedback. The Software may periodically submit statistics about its
operation to servers operated by MailChannels and other parties
authorized by MailChannels (the “Feedback”). The Feedback shall
include but not be limited to the IP addresses of email senders,
server memory usage, server CPU usage, and various attributes of
email sending hosts such as operating system type.

Exhibit #2 – Stream capture : feedback.mailchannels.com port 25 gets sent a log line per email as a http post.

rd.42946-feedback.mailchannels.com.00025: POST /et/capture HTTP/1.1
Host: feedback.mailchannels.com
Content-Length: 402
Connection: keep-alive

[2008-05-25 16:58:53 +0100] [22019] i=78.149.112.169:52371 h= o=N u= a= t= p=0 d=0
x=”ClientACL t=0,0|EarlyTalker t=0|RBL action=reject;cbl.abuseat.org=no_data;hul.habeas.com=no_data; query.bondedsender.org=no_data;sbl-xbl.spamhaus.org=no_data; t=0.11,0.17,0.04,0.28,0.17;zen.spamhaus.org=127.0.0.11.reject”
l=ACCEPT c=550 z=”Found on zen spamhaus” e=”[550,Found on zen spamhaus]”
q= n=1/0/1 b=0/0/0/1 v=

^{CR’s added for readability}

I completely understand why they want the spy-in-the-box (having worked with Justin I know the possibilities are endless) but that license is a bit too lax for me. It’s just a niggle but I’d feel more comfortable if it was defined explicitly, and explained in full and have the option to disable it on privacy grounds.

You need to disable SPF in your mailserver too, since the postfix sees the proxy ip, spf hard fails result in a reject … I should have thought of that Maybe thats where my license file has gone Woops.

Just in case Ken reads this..

• Kudos for the non commercial licensing


• I’ve mailed free-beer and am still waiting for a key.

Being a typical old school QA guy I’ve a heap of suggestions, but for the time being this image of my mailbox shows the performance in the first hour or two with the default config.

...eww, but you should see what happens without it.
In fact if you look at the graph below you can see the effect is that the server is relaying more mail and rejecting less.

^{E&OE plus the fact I’m in a rotten mood, I’m blaming the prescription(s)}