Have you tried setting the REPLY TO address in your identity? I think that will work.

Thank you for replying. I so much appreciate it!

Yes I have set the reply to address at the identity, and when the recipient clicks to reply, it comes to the right address. However, the header of the email that they see says From: lln****@gmail and not c****j@pobox.com.

See the picture below. I sent this email titled "delivery test" to Jane Doe who has an Office account. This is what she sees. The email she sees is my IMAP, not the identity I sent it with. However, if she clicks reply, it does send to the correct @pobox identity.

My goal is to get the IMAP email to disappear and be replaced by the identity.

The second picture is from Thunderbird under manage identities.

Thanks again for your help!

Are the pobox addresses actually aliases of your gmail account? The pobox website indicates that their email ids are valid email accounts. An identity in TB is an alias. I set up an alias to my own account and it works as intended. So, if the pobox ids are actually just aliases, then you may have an incorrect setting.

With pobox.com you can have up to 3 addresses, but they are are forwarded to one email. I have pobox sending all email to the gmail account. Then the gmail account is IMAPPED to Thunderbird. When emails come in, I have filters set to put each of the 3 addresses in a different folders. (One address is for junk stuff, so I can ignore that folder, one address is for personal stuff, and one is for business stuff.) I like the organization of having three folders in my inbox to sort stuff.

When I reply to any email, it looks like the attached picture and used the right identity/address. However, when the recipient gets it, the gmail address shows on their end. (This is true for new messages as well as replies.)

Again, THANK YOU for trying to help me. I hope I am able to give you enough information.

Sorry if this is a repeat. I posted a reply and then it seemed to disappear.

Pobox allows three addresses but you have to forward all of them somewhere. I have three pobox addresses that are all forwarded to the gmail account. I have 3 folders in TB, and incoming mail is sorted into those folders based on which pobox was used.

When I send new mail or reply to incoming mail, the pobox shows. However, the recipient actually sees the gmail.

THANK YOU. Your time trying to help me is much appreciated. I am happy to share any other pictures of settings as needed.

Well, what you're doing is unusual, but it does work, at least a bit. You might try adding the smtp server for pobox to the identity definition. On the positive side, that would create a legitimate sending: the email id would be pobox and the sending server would be pobox. I tried to imitate what you want and my tests have worked as intended. Does the gmail account setting use a REPLYTO entry? It should not. Please try the smtp server suggestion and see what happens.

So you are saying I should change the red arrow part in the picture to the pobox address?

That won't mess up the IMAP?

No. I am suggesting that you add the pobox smtp server at accountsettings>Outgoing servers, and then add that also to the identity pane and try that. It may do what you want. And if it doesn't, it's easily removed. DO NOT change the gmail server settings.

THANK YOU!!!! That fixed it. I really appreciate your time.

You're welcome. I'm pleased it works. However, I will share that I do not see the benefit of sending the messages through gmail. You could accomplish the same by just using a pobox account with two identities.