All responses are emailed....

Fundamentally you will need to contact the relevant account providers for your password resets. Thunderbird has no copy that can be accessed except those stored on the local machine.

Thanks for the reply. My initial need is in fact to get back into Thunderbird. The risk of losing lots of relevant material by attempting to reset/delete a master password that might not exist terrifies me.

PS to Matt. The Thunderbird password on the newer PC was not to my knowledge changed from that on the older one, so my correct password should be accessible somewhere in Thunderbird on this older PC (I think). Most of the passswords I can access in the Passwords file have not been changed and I can access sites without difficulty, hence my disinclination to try to delete/change a primary password. The Thunderbird password does not appear to be stored in that file.

PPS, Searching "updateThunderbird password" I have found passwords. The one for my main email worked, two others didn't but they were rarely used so the problem is adequately solved. N

I spoke too soon, whilst I managed to access my main Thunderbird account yesterday, I omitted to click on the store button and have had no success today. I have frequently substituted numeral 1 for letter l and numeral 0 for o when creating passwords but no permutation of the options seems to work today. I think I am also confusing myself between Mozilla and Thunderbird passwords and am now getting desperate for an answer. For Thunderbird to reject my attempts, it must be refering to a passsword somewhere, is there no way it can reveal it?