Sorry, just noticed: the title relates to my problems on the W11 install but thought I'd better start at beginning.

Apparently it's trying to load the welcome page. (I've got chat turned off) I've cleaned the registry. I don't have BrowserSafeguard installed. I've just removed IBMTrusteer Rapport as that might be a bit similar. Still getting the error. Also get the same error if click on "Learn more about Do Not Track" in Options/Privacy.

The next error is that it says it (31.8.0) is the latest version so I'll have to manually upgrade. Automatic updates is turned on. (Perhaps it's just too old?) Should I go one major number at a time, or jump in with the latest?

Thanks

OK, the error was from it trying to download the wlecome page. Seems to be a problem with out of date certs in the old TB (or maybe on my old PC). Anyway, I've upgraded to the latest version of TB and it all seems to be working. Now to move to new W11 PC.

Some issues.

1. Why on earth are you messing with Thunderbird 38. There was a time when it was about the only way to import outlook PST content to Thunderbird until bug in the importer were fixers years ago. Now not so much.

2. Avast offers instruction on how to force Thunderbird to use it's self signed certificates. Personally I find the process rather poor security. The certificates are issued in a chain of trust, Avast chooses not to have their business audited and meet the costs of same to be included, so ask users to reduce their security so the company can hack into your communications.

3 The certificates that will be offered will be current, what is happening is a web page is loading and the web server has current certificates as the same thunderbird.net server is used for all versions of Thunderbird. The problem is Avast substituting the certificates issued by the web site for it's own which Thunderbird rejects.

4 Uninstall Avast and try both your W11 install and Thunderbird and be pleased how all your issues suddenly cease. Not removing avast in Windows 10 and 11 will activate Windows defender. So you are not on windows without an antivirus.

To be honest defender is all I use after paying for products that slowed my devices, messed up communications and drove me almost mad with false positives for the proceeding 20 or more years.

AN FYI, this is some of the Avast issues that have been documented in relation to Thunderbird. Although the updating of the wiki is very patchy these days it does not inspire much confidence. https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#AVAST

Thanks Matt. 1: I'm new to Thunderbird and the posting on migration that Google found for me said that you had to go back to 38 to import from Outlook: https://support.mozilla.org/en-US/kb/switching-thunderbird. I took this to be the official recommendation from Mozilla. You'll notice that the article is undated.

2: I use Avast but yes, I'm always suspicious of companies that are selling higher levels of security cos there's always an unstated "trussst in me..." clause and never any info on their internal security policies, employee vetting procedures etc. (Russian or Chinese antivirus anyone?)

I'd already seen A: that 38 thought it was current and refused to upgrade itself, and B: after exporting certs from Avast and importing into TB, they still weren't visible in TB - so this created an expectation of problems to be solved. Perhaps if things had gone smoothly from the start I'd have back-tracked rather than trying to fix.

Anyway once I'd figured out how to upgrade properly and port properly, it all went very smoothly, all the certificate issues disappeared, and it now works fine.

So thanks again.