See if Chrome browser needs updating.

My browser (Chrome) is fully up to date.

you are using windows 1q0. It has a habit of messing with "default" applications often when it is updated, like turning cortana back on. I suggest you install Firefox, let it become the default browser and then install chrome again. I think you will find both will work fine with links.

Matt said

you are using windows 1q0. It has a habit of messing with "default" applications often when it is updated, like turning cortana back on. I suggest you install Firefox, let it become the default browser and then install chrome again. I think you will find both will work fine with links.

I tried this, it didn't work. I also tried changing the default to edge like was suggested, and back. That didn't work.

I checked everything in this article except the general troubleshooting which is a lot of work for a simple bug. https://support.mozilla.org/en-US/kb/hyperlinks-in-messages-not-working

We wrote a support article that addresses all the factors related to thunderbird.

It does not fully explore the junk aware anti virus product folks install, nor does it consider the use of a VPN to spoil everything except pirate television viewing.

It does not look at the vagarities of the operating system or the malware that can cause these sorts of issues.

There are three components in passing a link. one is Thunderbird and to be honest unless you change the default settings for security or install software that does. Thunderbird always just works. However actions taken occur frequently enough that we wrote an article, regardless of the cause.

The second component is the anti virus product. These tend to intercept all links and compare them to their list of "bad" sites. In the process they very commonly turn what is normally a simple click into disaster. SO we get folk in support forums looking for help with their anti virus products because is is not the anti virus product that is not working correctly.

The final component is the operating system. Windows 10 has a lot of quirks and foibles and actually setting a default web browser other than edge is far far more difficult than it should be. If fact I have found it impossible to entirely loose edge, it just appears at random intervals and usually pretends to be something else like twitter.

However I digress The standard diagnostics that you are linked to from that article are basically the same as what I will include below in many regards, they are designed to remove an add-on that might be malfunctioning or some high level feature like hardware acceleration. That is Thunderbird safe mode. Windows safe mode is basically to convince the unbelievers that their anti virus product really is the issue, or at least the issue is not Thunderbird. ____________________________________________________________________ To diagnose problems with Thunderbird, try the following:

• Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.
• Restart the operating system in safe mode with Networking. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, OSX

If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.

Add-ons disabled nor safe mode fixed it. I had given up trying to fix this while I awaited a reply. However, that evening my computer rebooted; I think I got a Windows 10 update. Then overnight I made an image of the hard drive. And the next morning the links were working in chrome!