Is this on a single laptop with two unique users?

If you have one user and two or more accounts within Thunderbird, one for yourself and one for your husband, the email address populated by the 'From' field at the top will be the highlighted account when you click on the '+ New Message' button.

I don't know what you've checked so please look at these:

The email address associated with the account is accessed by going to Hamburger icon (top right)/Account Settings and then click on the name of the Account (at the top of the list of settings). The email address is in the right pane.

When you click on '+ New Message' to open a new window, is the email address correct in the 'From' field? If it isn't, use the drop down to amend it.

Thank you for your prompt reply. We are using a PC Our Gmail accounts both come down to Thunderbird in separate inboxes. I am the main account holder. Recently replies to my husbands emails are coming to my inbox. His name is in the from box when he emails but arrives as though it has come from me. A friend who we emailed tonight confirmed this, and said that his email looked as though it was coming from my email address.

Please comment on the advice I gave you and if it is a solution. And confirm that you have checked the settings requested. Thanks.

In account settings with my husband's account showing, opening a message says it is coming from me. So now I see what the problem is, but I don't know how to change it permentantly.

In account settings with my husband's account showing, opening a message says it is coming from me.

When you have 'Account Settings' open, you can't open a message. You would have to do that in the main window.

Would you post a screenshot and circle what is the problem as I'm not sure where you're looking in TB.

This is an old PC a bit like me so I don't think I can do a screenshot as I would from my smartphone.

I have taken 2 photos and attached. I don't know how to mark them as I used my camera and downloaded the photo to the PC One is my husband's account settings page; the other is where I can click on new message from his settings page but the recipient would still be replying to me as I tested it with my yahoo email address.

I rather think that I shall have to see if someone locally can help me especially as it is getting late here in the UK. Apologies for not being very computer literate and thank you for trying to help.

Okay. Thanks.

I don't actually see the problem that you're referring to - it all looks okay. Did you go through my original reply and look at how the sender's/reply to email is determined by the account that is highlighted when you click on 'New Message'? I still think that this may be what you're doing.

"If you have one user and two or more accounts within Thunderbird, one for yourself and one for your husband, the email address populated by the 'From' field at the top will be the highlighted account when you click on the '+ New Message' button."

And it's getting late here in the UK, too.

When new mesasage is clicked from David's account it appears to be going from him. This problem has only started recently so I am mystified. I shall have another think tomorrow. Thank you very much for your help and suggestions.

When new mesasage is clicked from David's account it appears to be going from him.

It will do. It may be that you're not quite grasping what I'm saying.

With ONLY the normal interface open: 1. On the lhs in the tree under '+New Message', something will be highlighted. 2. That selection is displayed on the right. 3. Let's suppose that the highlight on the left is under YOUR account. Your husband comes along and thinks 'I need to send a message' so he clicks on '+New Message' and fills in the recipient and so on. 4. Because your account is highlighted, the new message has your account as the sender and 'reply to', NOT his. And who checks that, anyway, before it goes? Even if you have separate address books. It will only ever use the sender's email address from the account that's highlighted.

Is that making it clearer? That's what I think is happening.

How To 'Screen Print' tutorial - https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem#w_create-a-screenshot-on-windows

I think the problem is that you don't have the accounts set to send on separate smtp servers that have User Names that match the sending account. For example, if gmail account A sends on the smtp for gmail account B, recipients will see messages sent from A as if they were sent from B. So replies will go to B.

https://support.mozilla.org/en-US/questions/1438310

https://support.mozilla.org/en-US/questions/1350593