remove norton. I think you will find it to be the problem child. It as a smart firewall that is not.

Tried removing Norton but it made no difference. I had the same Norton software on my previous laptop which worked fine with Thunderbird.

Thanks for the advice.

remaining possibilities.

Nortons removal was not complete. Did you use their removal tool? https://support.norton.com/sp/en/au/home/current/solutions/v60392881_EndUserProfile_en_us

Your WiFi Router is blocking the ports used for email. This is most often old devices. But it could be the case with some ISP issued devices. Comcast I think it was, some years ago change mail ports to a port their own modems blocked. So check the settings on the Wifi Device that it is not blocking the ports used.

Help menu > troubleshooting information will give you a quick account overview with the ports being used.

Well, my email has started to work now. All I did was reinstall Norton, not thinking that that would change anything but as I had paid for it I might as well use it.

I do not know what changed and still do not know what was causing the problem other than a possible Norton/Thunderbird clash. I not really that happy not knowing what the exact problem was as I can't check on it if the problem were to come back.

So thanks for the help and hopefully I will not need to come back to this post.

The problem will almost certainly have been the firewall that came with Nortons. Probably twenty years ago I have my first encounter with windows firewalls as a trial that I allowed to expire. When I uninstalled it it simply did not reset the firewall so the ports it blocked remained blocked until I installed another which reset things to the defaults when it was installed. To this day I do not know how or what it left, I assume registry entries that had windows basically continuing to "firewall" without the ability to control it.

One of the issues we all face with out anti virus products is they are all battling to remain relevant in an environment where there basic functions are being offered by windows so like the swiss army knife they keep sprouting new functionality. Firewalls, identity safes, phishing protectors, spam filtering unfortunately they and like the swiss army knife. They do the job. Sort of. But the right tools for the job would be better quality and much nicer to used and do the job better. Anti virus product occupy a very privileged position. Both in terms of access on your device (system level, the highest, Integrated with the physical hardware) and in our hearts. We have to trust them to do the job. Unfortunately they are not worthy of that level of trust.

We see it all the time here, anti virus crippling mail reception. Nortons is always high on the list of those mentions, along with McAfee. One is packaged by a Major US ISP and the other is bundled with Dell computers so the frequency of report might be about penetration into the market. Or it might be a reflection on the products. I don't know. I just know I would not use either any more and over the years I have used a number of Anti virus products. Only one thing really is common almost universally, and that is marketing hype that promises security and is more adept at half truths and scary warnings.