It used to work for TB2.
For TB3 I now just have a message "does not provide secure updates" in the Add-ons screen.
I tried adding boolean "extensions.checkUpdateSecurity=false" as outlined in mozillazine but it does not seem to work.
see
kb.mozillazine.org/Extensions.checkUpdateSecurity
We can't really help you on this one as it's an issue with Thunderbird itself rather than Thunderbird Portable. I don't know what the issue is.
I am a Christian and a developer and moderator here.
“A soft answer turns away wrath, but a harsh word stirs up anger.” – Proverbs 15:1
Your best bet for help is over at the main thunderbird development forums for that one.
As far as I recall, it is either that the addon update URL needs to be over https, or that the xpi needs to be digitally signed.
You could try installing MR Tech Toolkit, it used to have an option for overriding that problem.
Yeah, the security was a good idea in theory, but it seems like it'd be a nightmare for extension developers. It'd be like if your OS wouldn't run any programs unless they were digitally signed, how could you test and debug your own programs then?
seems to sum it up... I have a zip of it all, I will rename it to xpi and see if it goes on as an install rather than a straight copy. No high hopes though.
I always got to the distro part and went 'meh'. Maybe this security is also partially to force people to research how to release their extensions? rofl
https://developer.mozilla.org/en/McCoy