Do you where "Contacts" came from? It is not a native Thunderbird address book, so must be the result of importing from somewhere else, or is a view of an external address book.

Are you using a Mac? Thunderbird can use the Mac address book, but at one time it was (and may still be) a read-only connection.

Please note that in Thunderbird, a "List", or in full, a "Mailing List" is a specific group of Contacts similar to a Group or Distribution List in other mail clients. I'm guessing that you're not using "List" to mean one of these.

I use to click on Address Book and it gave me three options: Address Book, Contacts and Personal Addresses. Now it only allows me to add names to Address Book. Could this have happened when I downloaded Windows 10?

You haven't told us where "Contacts" came from. So we don't know if this is read-only or not.

I am confused by your descriptions, but maybe you're working with a non-English version of Thunderbird?

We have a "new" address book, named All Addresses. It isn't a real address book, but a virtual address book composed of all the other real address books. You will have two real address books by default, Personal Address Book and Collected Addresses. Any others were created by you, either deliberately or via importing from somewhere else. I'm using the default English language names here, but conscious that the names might be slightly different in translation to other human languages.

You can't add contacts to All Addresses. You must add them to one of your real address books. What do you mean when you say "it only allows" you to add to "Address Book"?

If you're allowed to add a Contact but it isn't there after you close and restart Thunderbird then you have a specific problem with an address book being corrupt. This can be repaired by exporting it to an LDIF file, deleting the original and re-importing it.

But so far I have asked you two explicit questions.

• Are you using a Mac?
• Do you know where Contacts came from?

My contacts list was set up before I downloaded Windows 10. Evidently Windows 10 has a different Address List system. Now I need to know how to transfer my current contacts to Windows 10 Address List. I think this is the problem.