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Block Constant Contact

Written: Apr 13, 2013

While 'legitimate' email marketers like Constant Contact claim to be 100% opt in totally not spammers, in my personal experience, the only thing I ever seem to get with a Contsant Contact SafeUnsubscribe button is spam. I've written them about it before and they want you to forward the full headers and seem all concerned, but a few weeks later, yet another spammer using Constant Contact shows up in my inbox. And, to be more annoying than most 'legitimate' email marketers, you have to enter your email address in a form after you click their unsubscribe link. This makes it extra-annoying for people who use aliases or # addresses as after you click, you have no idea what email address they need and have to go digging around in the source email to find which of your addresses were harvested or stolen.

Blocking Constant Contact

Since I've never gotten anything I care about from Constant Contact and I'm sick of using their convoluted unsubscribe process, I decided to just block them. Luckily, it's relatively easy to block them using any of the distinct bits in their email headers. Here are a few of the things you can block on:

  1. Sender: The Sender in the email headers will be in the vein of [email protected], so if your server-side filtering software lets you filter on a variant of sender, you can just drop anything ending in
  2. Received: Your server will get the email from ccm?? where the ?? is the mailing server #. You can either block on that or just on and be done with it.
  3. X-Mailer: Constant Contact uses a custom X-Mailer client of "Roving Constant Contact 2009 (". You can filter on a portion of that string to block.
  4. List-Unsubscribe: The List-Unsubscribe header will be something like and then a long string of characters, another unique item to filter/block on.
  5. Netblock: Constant Contact owns the range of IP addresses -, so you can block on those to kill off the emails. I'm unsure if they own additional ranges or not.

That's That

And that's that. Use one of the above and never deal with Contsant Contact spam again. If you block entirely by using the netblock, the sender using Constant Contact will know about it. If you filter internally, it's likely that Constant Contact will report it as successfully delivered (technically it was delivered to you, just to your circular file).