Gmail automatically copies sent messages to the Sent Mail IMAP folder, so you should uncheck 'Place a copy in' in Tools/Account Settings, Copies and Folders, for the account. Then, right-click the account in the Folder Pane, Subscribe, and make sure Sent Mail is checked, i.e. subscribed.

Thank you sfhowes for responding so quickly.

In each profile, I opted for Thunderbird to put a copy into the "sent" folder that is within each gMail account.

It's a lot of trouble, but I clear my cache before I close my browser. This morning, I logged into my gMail account online for one of the accounts under discussion and printed out an email from the "sent" folder.

I closed the gMail window, cleared the cache, closed the browser, reopened the browser, and opened the other account to its "sent" folder. Except for my email addresses being different on them, the Subject and Body of both emails were the same.

Code somewhere wrote copies of the (single) email to (both) of the "sent" folders in the gMail accounts.

I'm waiting for a response from the individual I sent the email to. Calling him during work hours is not physically possible!

Any suggestions will be greatly appreciated. Even known "guesses" will be appreciated!

More: I did change storage defaults. That was an obvious thing to do. My intent was to say that I had not changed what Thunderbird's defaults accomplished.

Not sure what you've done. By default, TB has the 'Place a copy in' box checked. This is incorrect, because gmail automatically copies sent mail to Sent Mail. You should uncheck 'Place a copy in' in TB for all gmail accounts and see if sent messages are stored in the correct, Sent Mail folder. The Sent Mail that you subscribe to in TB is the same as the Sent folder shown on the gmail website.

If you send a message from the gmail website, is the sent message stored in one or both accounts' Sent folders?

FOLLOWUP: To keep the accounts separate in my mind, I had the background color of the pages colored differently and the desktop setups looked different.

The receiver of the email has been heard from. I sent the request that he tell me how many copies of the subject email arrived in his email's inbox. The request was sent with "Profile A" and he responded with a "reply" and it came in on "Profile B"

My original use of Thunderbird was to have it installed on my computer and used with one account; No problems.

When I send an email from gMail's website, it goes into the "send" email box online.

On the "Copies & Others," I've selected the email online account for storage and that is where the sent emails appear. Thunderbird downloads the "sent" box from gMail.

sfhowes said

Not sure what you've done. By default, TB has the 'Place a copy in' box checked. This is incorrect, because gmail automatically copies sent mail to Sent Mail. You should uncheck 'Place a copy in' in TB for all gmail accounts and see if sent messages are stored in the correct, Sent Mail folder. The Sent Mail that you subscribe to in TB is the same as the Sent folder shown on the gmail website. If you send a message from the gmail website, is the sent message stored in one or both accounts' Sent folders?

Regretfully, I didn't answer your last question. When I send from either account, it goes into the sent folder for whichever account I'm into online.

If you send a message from account A, and the recipient replies and the message goes to account B, that suggests A is sending on a gmail smtp with B's User Name and password, as that is what gmail does - it switches the sending identity to that of the smtp. Tools/Account Settings, select account A in the left pane, then click Edit SMTP server in the lower right pane and see if the User Name for the smtp is the same as the User Name for account A.

Let me repeat once more: uncheck the 'Place a copy in' box for all gmail accounts as in the attached picture.

sfhowes said

If you send a message from account A, and the recipient replies and the message goes to account B, that suggests A is sending on a gmail smtp with B's User Name and password, as that is what gmail does - it switches the sending identity to that of the smtp. Tools/Account Settings, select account A in the left pane, then click Edit SMTP server in the lower right pane and see if the User Name for the smtp is the same as the User Name for account A. Let me repeat once more: uncheck the 'Place a copy in' box for all gmail accounts as in the attached picture.

I can do that, but for legal reasons, I need to be able to refer to what I sent. Of course, CC could work or even BCC.

I'll work something out. Thanks for the help.

If you apply the setting in the picture in my previous reply, sent messages will still be copied to Sent Mail, and you will avoid duplicates and other issues. Automatic copying of sent mail is a feature of gmail, outlook.com and a few others.