Did you try the method explained here?

http://kb.mozillazine.org/Master_password#Resetting_the_master_password

Sam said

I found an article how to reset the master password. It worked for Mozila's password in the browser but not with thunderbird. I cannot get it to go to thunderbird's tool to reset it from there.

Yes I did but wasn't helpful. the method helps if thunderbird already opened

sfhowes said

Did you try the method explained here? http://kb.mozillazine.org/Master_password#Resetting_the_master_password

Yes I did but wasn't helpful. the method helps if thunderbird already opened.

At the bottom of the article it suggests deleting or renaming key3.db from the profile folder. In current versions, the relevant file is key4.db, and it can be deleted or renamed along with cert9.db (security certificates) and logins.json (passwords). You'll have to re-enter your account passwords.

The default location of the profile folder is: C:\Users\windowsusername\AppData\Roaming\Thunderbird\Profiles\eightcharacters.default

@sfhowes, Thanks for your help.. It worked.

Sam said

@sfhowes, Thanks for your help.. It worked.

I have spent hours, even days, with problems of both themes and passwords.

A theme set in Firefox poured over into Thunderbird. I managed to fix that in Firefox but that them has rendered Thunderbird virtually unreadable.

The "best answer" may work, but NO user should have to fish around for hours to find and implement a programming glitch.

RonKZ said

I have spent hours, even days, with problems of both themes and passwords. A theme set in Firefox poured over into Thunderbird. I managed to fix that in Firefox but that them has rendered Thunderbird virtually unreadable.

Start TB in safe mode (hold Shift when you launch TB), then go to Tools/Add-ons/Themes and Remove the problem theme, then restart TB in normal mode - the default theme will be applied.

I have forgotten a bit of my master password and cannot login to TB. I am using TB in Linux.

The article cited..... http://kb.mozillazine.org/Master_password#Resetting_the_master_password .....refers to an Evaluate button. But there is nothing referring to Evaluate on my Error Console.

How do I proceed please?

The Evaluate button doesn't appear in my version either, TB 60.7, so it looks like it was removed. Does it work if you press Enter? Otherwise, you can delete the three files from the profile mentioned above.

Sorry that I have not re-posted earlier - I have been away. Many thanks to SFHowes for your interest and help with my issue. In the following I give a rather long account of the issue. Sorry to be long-winded but I hope that something may be of help or interest to others. I tried many times to enter or change the Master Password in Thunderbird, without success. I did write down the MP when I first created it, but TB refuses to accept it. I tried many variants of the MP in case I had mis-keyed a character, with no success; and of course the probability of the same mis-key being entered in both fields on the creation window is very low indeed. I am beginning to wonder if there is a bug in TB regarding the MP. So I am now exploring the possibility of cracking the MP - I am trying to discover if the Firemaster software can be used for TB as well as Firefox MP. If so I will give it a try. Failing that I will be forced to re-set the MP, according to the method shown in the Mozillazine article. For interest, in my version of TB ( 60.7.0 64-bit )the path to the point of input for the text that must be entered is as follows : Tools - Developer Tools - Error Console - and then a window appears that has the heading Browser Console, and there is no Enable button. I do not know if this is the correct path, or if there is something amiss with my app. I will report the progress/outcome of my actions. Tom.

Keep in mind that the 64-bit version of TB is not officially supported, and it may have bugs that don't appear in the 32-bit version.

As mentioned, the Browser Console doesn't have an Evaluate button anymore, as I expect pressing Enter does the same thing.

So to update and close my contributions on my issue......

First, I received no response to my query about whether Firemaster can be used to crack the master password in Thunderbird (I can find no info. to suggest that it can; only Firefox MP is documented.)

So in a last desperate attempt to get the correct password, before going through the reset procedure, I played around for some considerable time with variants of the MP that I had written down. And surprise! I eventually hit on the correct combination of the few keys (I knew about 20 of the correct characters) that completed the correct password, and I was into my TB emails. Success!

So I cannot testify as to whether the enter button substitutes correctly for the missing Evaluate button in the console.

I close with my sincere thanks to SFHowes for your interest and help. TJP.