re 1) forwarded letter has an original "From" field

If you are forwarding an email either manually or via an automated filter, the FROM will be your email address because it is forwarded FROM you.

re 2) forwarded letter has added a "reply-to address" field containing sender address automatically.

As you are the 'Sender', you must add your reply-to email address into your account settings for the mail account. Then it will use your settings, but this will then apply to every email you send.

You cannot and should not use other peoples email addresses to send emails. If you receive an email from someone, they are not giving you permission to use their email address for sending out emails in their name.

I have another purpose.

Maybe this add-on could do what you want: https://addons.mozilla.org/en-US/thunderbird/addon/mailredirect/

…but I don't know how to get a filter to do Mail Redirect.

But the smart way to do this is to set it up at your server. It may offer a "forward" option which behaves as you want, whereas "forward" in a mail client assumes ownership of the message and inserts a relevant "from:" address.

Add-on MailRedirect and Thunderbird filters is not compatible.

>> But the smart way to do this is to set it up at your server. It is right, but our email don't have a web interface.

let me get this right, you have what I can only assume are web sites sending you mail and you want that mail to go to a third party with the correct reply to address, which I assume is the person making the inquiry.

I just do not get this, sounds like your trying to use Thunderbird to make up for deficiencies in your web site.

Sounds like this: you have a webpage which people may send an email to your server email address, so the FROM will be the person sending the email and the TO will be your server email address. Then you want the email to be forwarded to a person within your organisation so that the email now says TO that person FROM the server email address with a REPLY-TO the original person who sent in the email. But when you do this and click on 'Reply', the Reply-to is not inserted into the TO, instead the FROM server email address is inserted into the TO.

Does this describe the issue?

Maybe.

Summarized: Email forwarding removes original sender's email address.

I want to have original sender's email address in "TO address" field or "REPLY-TO adress" field after forwarding through the Thunderbird filter.

"Email forwarding removes original sender's email address." - well, yes, of course, if you do the forwarding in an email client. It can only send from whichever account is used to send it. Mail Redirect can emulate the way servers forward by use of Re-Sent fields in the header.

"I want to have original sender's email address in "TO address" field or "REPLY-TO adress" field after forwarding through the Thunderbird filter." - well, the first bit is silly. The To: field must contain the address it is being sent to, not the address from which it was sent. Technically, I guess the Reply-To field could be used, but as you have found , the filters don't offer to fill this in for you.

You really do need to be doing this at the email server.

Sorry "I want to have original sender's email address in "FROM address" field or "REPLY-TO adress" field after forwarding through the Thunderbird filter."

I'm not sure what it is that you not understand. In Thunderbird, you cannot use Forward and put the orginal sender into the FROM because when you forward the email it is not FROM that person, it is FROM you.

Option 1: You need to set it up from the server to insert the orginal FROM into a REPLY-to.

Option 2: download and use this addon:

• https://addons.mozilla.org/en-US/thunderbird/addon/mailredirect/

Workaround 1: tell the person/developer who wrote the website email form to auto put the FROM into a REPLY -TO, so that it is already inserted when you receive the email. then if you forward it, although the REply -to will not be in the REply-to of the email, it can easily be copy pasted from the content header into a TO field.

Workaround 2: Write a new email and attach the orginal email as an attachment and send to other person. they can then right click on the attachment and choose to 'import message in this folder' then it would save the FROM and To, so that when they 'REply' it will insert the correct FROM (original sender) into a TO field.

Add-on MailRedirect and Thunderbird filters 'is not compatible'.

Purpose: Automatic Email forwarding. Manually - no problem (copy From address to Reply-to address field).

I have a mail server and CMS with limited functionality. Currently it can not be changed.

Only need to add a Reply-to field in forwarding email letters.

P.S. Is there a answer emails constructor Thunderbird addon?

use this add-on https://addons.mozilla.org/en-US/thunderbird/addon/filtaquilla/ with javascript to achieve what you want.