I may be misunderstanding your request, but this may help: - click settings>privacy&security - click 'saved passwords' and then 'show passwords' - highlight your account row, rightclick and select 'edit password'

Thanks David. I was aware of that but my problem is that the relevant account listing has disappeared from the 'saved passwords' table. The associated emails remain in Local Folders though. Ideally I'd like to retrieve the lost details, then I could (hopefully) update the password. I could create a new account, of course, but then not associated with the relevant emails.

What error messages do you receive when attempting to retrieve mail?

No error messages appear when attempting to retrieve mail. Thunderbird just doesn't appear to look, based on the fleeting display of account name bottom left. I do have a second account listed, not based on the Local Folders, and that is working fine, so I presume there is no issue with Thunderbird itself

I think you need to check the account settings for the authentication method to be used. Note: Yahoo Microsoft (MSN,hotmail, live and outlook) and Gmail all require oauth authentication, in those instances there is no "password" only an oauth line in the password manager that contains a "token" issued by your provider in the initial authentication process. It is not your password. Although if deleted, or denied by your provider (lie they forced a new password on you) it should initiate a new authentication web page flow. I have seen these pages variously described a a bug, a nag screen and one person thought they had been hacked. Many simply ignore them and then complain about non receipt of mail.

So what authentication method are you using and what mail provider are you using it with?

Thanks for your suggestion Matt. My mail provider is The Messaging Company, in Australia. My account settings (server name, port, security, etc) all seem to match their recommendations (I have checked and rechecked). I do need and have a password, and it works to login to their webmail. I was required to change this password (for other reasons) and have done so. Then I obviously had to change it in Thunderbird in order for emails to sync/download (I am using POP, not IMAP) but that is where things have gone awry, somehow. There is now no line item for the provider's server which I can update the password for, and I cannot see how to add or create one. I could create an new account of course, but the default for that is IMAP, not POP, and Thunderbird won't allow you to change server type. I have tried manually setting up a new account, but I am prevented doing so at the last hurdle because Thunderbird notes the email/sever combination already exists. And even if I do this, I don't know how to link my 1000s of stored emails in multiples folders to the new account for continuity. So, still stuck.