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We learned a valuable lesson after sending our most recent monthly newsletter, which we’d like to share. It turns out that our friends using the Mozilla Thunderbird email client had their newsletters prefaced with the alert, “Thunderbird thinks this message might be an email scam.” It looked something like this:


Of course, we weren’t trying to scam anyone with our monthly dose of email tips and app updates… So what had we done wrong?

After a bit of tweaking, we discovered that Thunderbird systematically throws up this alert when it sees a URLs in your HTML email copy. This is also an issue that similarly affects Outlook and Entourage email clients, too. In this case, we had made the mistake of adding the following line:

If you would like to support the National Wildlife Federation in protecting wildlife and their habitats, kindly donate at

Big boo. Although adding a text link doesn’t explicitly set off any spam filters (i.e. your email will still get delivered), the alert could potentially be enough to put off some readers. When we changed this line to…

If you would like to support the National Wildlife Federation in protecting wildlife and their habitats, kindly donate today.

…Thunderbird calmed down. Well, that’s something we won’t repeat.

Another approach is to append your links with cm_dontconvertlink, as phishing alerts are often thrown when the URL in the email copy doesn’t match the URL (<a href="...">) it’s linking to. Adding cm_dontconvertlink tells our app to not make your link trackable (ie. leave it alone), so this discrepancy doesn’t arise. Here’s an example:

<a href="" cm_dontconvertlink>this is a link</a>

The obvious downside is that clicks on links like this won’t be recorded in your campaign reports.

The moral of the story is, don’t type out URLs in your email copy, or be prepared to turn off tracking if you wish to do so. Otherwise, the bird might just drop some of its thunder on you.

This blog provides general information and discussion about email marketing and related subjects. The content provided in this blog ("Content”), should not be construed as and is not intended to constitute financial, legal or tax advice. You should seek the advice of professionals prior to acting upon any information contained in the Content. All Content is provided strictly “as is” and we make no warranty or representation of any kind regarding the Content.
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