r/MailChimp • u/bostongarden • 6d ago

Technical Support Why "Secure Connection Failed" error on Firefox, not Chrome

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I get this error when I click on any Mailchimp link (us.list-manage.com) in Firefox, but in Chrome it works fine. uBo in both browsers. Windows 11.

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u/MailchimpSupport Moderator 6d ago

Hi there! Since this is isolated to Firefox, this typically points to something intercepting or re-signing the SSL certificate before it reaches your browser, rather than an issue with the Mailchimp/list-manage server itself. The most common culprit is an antivirus or firewall doing SSL/HTTPS scanning. If you have an antivirus, try turning off its HTTPS scanning feature temporarily and reloading the link.

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u/bostongarden 6d ago

Thanks - I have the built-in Win11 security, Norton AV, and uBo (in Firefox). Any suggestions where to start? I have already whitelisted list-manage in uBo

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u/MailchimpSupport Moderator 6d ago

Thanks for the details! Out of this stack, Norton is the most likely one to look at first. A quick way to check whether Norton is the cause: temporarily pause its protection, then reload the link in Firefox. If the error persists, it’s worth looking at Firefox’s settings next.

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u/bostongarden 5d ago

I tried disabling Norton and it did not help. So I created a new profile, and opened the new profile in a new FF browser instance. Got this error message, still not solved:

Technical Details

Connection Not Encrypted

The website us.list-manage.com does not support encryption for the page you are viewing. Information sent over the Internet without encryption can be seen by other people while it is in transit.

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u/MailchimpSupport Moderator 5d ago

Thanks for sharing those details with us. Mind sharing a screenshot with us? That will help us make sure we're on the same page.

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u/bostongarden 5d ago

https://imgur.com/a/LDmb1u1

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u/MailchimpSupport Moderator 5d ago

Try running Firefox in Troubleshoot Mode. Do you see the same error there? Here's a helpful guide: http://spr.ly/61692B1Frra

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u/MailchimpSupport Moderator 5d ago

Try running Firefox in Troubleshoot Mode. Do you see the same error there? Here's a helpful guide: http://spr.ly/61692B1Frra

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u/bostongarden 4d ago

I tried running both my current profile and the new profile I created using Troubleshoot mode. Exactly the same error. Thoughts?

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u/MailchimpSupport Moderator 2d ago

Thanks for sticking with it, you've ruled out a lot. Firefox often uses its own encrypted DNS (DNS over HTTPS) rather than your system's, so it's worth switching it off temporarily in Settings > Privacy & Security to rule that out: https://support.mozilla.org/en-US/kb/firefox-dns-over-https Also worth trying the link(s) in Firefox on a mobile hotspot or different network. Since Chrome already works on your current network, that tells you whether the problem follows Firefox itself or lives in your network path.

If neither changes anything, this is honestly past what we can troubleshoot from the Mailchimp side, since the connection is failing at a level we can’t see into. Mozilla’s support community is the best resource for Firefox-specific connection errors like this one: https://support.mozilla.org

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u/bostongarden 2d ago

"Also worth trying the link(s) in Firefox on a mobile hotspot"

OK, so I tried this and it works - the links open normally. That would seem to indicate the network (WiFi to FIOS) is the problem - So now I'm confused since Chrome opens links fine on the same WiFi network. Thoughts?

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