It all seems to be working quite normally as far as I can see. What did you expect it to do?

Red was correct as you say this correspondent wasn't already in your address book.

Perhaps I wasn't clear. It isn't about the red type for a new address. I understand that and it's not part of the problem.

Please keep in mind how many years I've used Thunderbird and that by now I certainly know what's "quite normal". What is happening now has to be the result of some instruction I entered in error. I just don't know what that was or how to disable it.

Normally, when I send an email, I first click Contacts, choose the recipient from the address book, then Subject, then my message, then SEND, and it's done.

Now, the instant I type the first letter of any destination email address, instead of letting me complete it, the system abruptly drops down my entire address book in the TO: box, which spills out over the message area as well. Stranger still, this drop-down version of my address book is sorted weirdly, according to the first letter I typed ("c" as I mentioned in my first query). In order to complete the address I intended, I have to type over the first item in the drop-down list so I can continue.

Until yesterday, if I was sending to someone not already in my address book, I'd just type the new email normally, without interruptions or drop-down lists. How could an unexpected, weirdly sorted address book possibly be useful at that point? How do I stop it from happening?

What version were you using prior to 45.5.1?

There was a change in address book searching a couple of years ago, and the change from a "starts with" search mode to a "contains" search mode startled many users. They seem to have got used to it, since by and large the complaints have dried up.

You just keep typing. As your entry becomes more specific, the offered list of possible matches shrinks. The search has been made more general allowing you to search on various parts of the email address. So you can now search the display name, the email address, (either local part or domain), and the nickname.

I don't understand how or why your selection of a Contact from the Contacts Sidebar should now be any different.

Thanks for your replies. I know you're trying to help. First off, I can't tell you exactly which version I had before 45.5.1. Updates seem to happen so often that I set things up to automatically update and seldom check to see what's changed as it's rarely major. That means that the change in address book searching you mentioned, if it happened a couple of years ago, I certainly have had since then. But I still don't connect that to my current problem.

I must have confused you further. At the end of your message you said you didn't understand why my selection of a Contact from the Contacts sidebar should be different. If you're talking about the "address book" button in the toolbar, it isn't different. NOTHING has changed. What has changed, only a day ago, is that I can't begin to type an email address, old or new, without being interrupted by the drop-down complete address book. Who needs it? It never appeared before. Why would I need it when I KNOW who I'm sending to and all I want to do is type their email address, finish my email, and send it.

It has ZERO to do with searching. That's what puzzles me. I just want to address and send an email as I have for years. No searching is involved anywhere. Regardless of updates, this was the norm until yesterday, or I wouldn't have submitted my query. It's not a new perk.

I know there are budget constraints, but if there were a phone number I could call, I'm sure this would be resolved in two minutes. It's oddball and difficult to describe via email. A screen shot might make it clearer. In any case, thanks, I appreciate your efforts to be of assistance.

Auto complete is not a new feature but I am coming to think that you have never used it and in the update process it has become enabled. (I am of the opinion that Thunderbird frequently changes or loses settings during updates. We have users who lose toolbars, or their connection fails, because some checkbox somewhere has changed its state during an upgrade.)

http://smallbusiness.chron.com/remove-email-auto-fill-thunderbird-63867.html

It hadn't occurred to me that it could be disabled, nor that anyone would want to.

I'm eternally grateful to you for that link. I've disabled the grinch that stole my address book. And you're quite right that I'd never have thought of using it in the past, so when an update enabled it I wondered where it came from. These update "surprises" happen every so often, and Thunderbird is by no means the only guilty one. It's fine as long as I know how to disable what I don't want, but that information isn't always displayed.

Thanks again for your patience.