From compose window, click view>toolbars and click 'composition toolbar.'

Thanks, David, but no. In Preferences/Composition,View/Toolbars displays, I see:

Mail Toolbar Menu Bar Folder Pane Toolbar Quick Filter Bar (Grayed Out) Status Bar

Customize

I don't see anything marked "Composition Toolbar" to click.

I said from compose window. Click the button to write and when compose window opens, you will see that option.

Thank you, David. I have now got my "send" button back. But trying to send a test msg, I can't get to the SMTP Server.

Can you help me with that? I have for Description: att.net / For Server Name I have smtp.att.yahoo.com / Port 465 / Connection security: SSL/TLS Authentication method: Normal password (same as I use to login to the AT&T website) / and User Name: is my AT&T email address.

Any suggestions for a change anywhere?

The first lesson every ATT mail user needs to get is that ATT/Yahoo refuse to allow you to use the same password on their web site and a mail client. You must use a mailkey. https://www.att.com/support/article/email-support/KM1240308/

Are you using a mailkey?