Can you add a new address? Is there an error when you attempt to edit?

I can add my son's new email address, but I cannot delete the previously added one, and I cannot edit it. When I type in his name, the system defaults to the now outdated original address. If I recognize this error at the time of the creation of the new email, I can correct the automatically posted but erroneous email address to the current one. But this is awkward and apt to be missed. Many thanks for help. John Clarke

See if you can edit another address. If you can, that indicates that his old address is somehow corrupt. That happened to me recently. SO, if that is the case, this works somewhat:

1. create an export of the addressbook in vcard format (export menu is at the three dots to the right of addressbook name)
2. open the exported file in Notepad and locate the full info on the bad address - delete all of that, but JUST that. be careful.
3. create a new addressbook in thunderbird
4. use the tools>import>import from a file menu to import the vcard export
5. verify that it's good and then DELETE the original addressbook

There may be better solutions, but this worked for me.

It has happened to at least 2 email addresses which have been changed by their owners. I accept that I don't know what is going on here, but I will attempt the solution you suggest, for which I am grateful. I may not get to it for a couple of days, but I will report back. Thanks again John

1. Open your address books in Thunderbird. (Alt+2)
2. Right click the address book name in the list of books.
3. Select properties.

Do you get only a dialog with a name of address book, or one with more details including a read only option?: