Here is the same thing with better formatting:

Under some scenarios the address headers are being populated in my draft reply to emails in a way that seems entirely erroneous. I am wondering if I can configure Thunderbird to avoid this, or whether Thunderbird needs fixing in this respect:

Scenario 1: In draft replies to emails forwarded by the server the REPLY-TO field is retained instead of converted to the TO field

Conditions of correct operation:

1. The server forwards all emails to enquiries@server1 to website@server1

2. The Mozilla client is configured to retrieve and send mail for website@server1

3. A website sends email1 TO website@server1 REPLY-TO enquirer@server2 FROM website@server1

4. The Mozilla user receives email1 and selects Reply

5. The TO field in the Reply is correctly populated with the REPLY-TO field in the original

Conditions of incorrect operation:

1. As above

2. As above

3. A website sends email2 TO enquiries@server1 REPLY-TO enquirer@server2 FROM website@server1

4. The Mozilla user receives email2 and selects Reply

5. The TO field in the Reply is incorrectly populated with the TO field in the original

6. The REPLY-TO field in the Reply is incorrectly populated with the REPLY-TO field in the original

Scenario 2: In draft replies to emails in a local folder the FROM field is incorrectly set to the default account instead of the original TO account

Conditions of correct operation:

1. The Mozilla client is configured to retrieve and send mail for user1@server1 as the default and user2@server2 as a second account

2. A correspondent sends email3 to user2@server2

3. The Mozilla user receives email3 and selects Reply whilst it is still in the user2 inbox

4. The FROM field in the Reply is correctly populated with the user2 inbox address which is the TO field in the original

Conditions of incorrect operation:

1. As above

2. As above

3. The Mozilla user receives email3 and moves it to a local folder before selecting Reply

4. The FROM field in the Reply is incorrectly populated with the default address instead of the TO field in the original

What OS are you using? What version of Thunderbird are you using?

To diagnose problems with Thunderbird, try the following:

Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). 'Help' > 'Restart with Add-ons Disabled'

If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.

Please post results. If you detect an addon causing the issue, please state the name of the addon extension.

Thank you Toad for your guidance. I was using Windows 10, Thunderbird 52.9.1 (32-bit) which gave the results above with or without add-ons disabled, as does Thunderbird 60.3.0 (32 bit).

OK, so let's try unravelling what is going on.... When you write a new message, Thunderbird uses the default identity for the account you are working in. When you reply to a message, Thunderbird uses the identity that matches the address the message was originally sent to, if it can find a match in the account you are working in. Otherwise it uses the default identity. I believe this may explain the issue when an email is moved out of the account into the Local Folder mail account.

CASE 1 works on Reply-to . A website sends email1:

• TO website@server1
• REPLY-TO enquirer@server2
• FROM website@server1

CASE 2 fails on Reply-to. A website sends email2

• TO enquiries@server1
• REPLY-TO enquirer@server2
• FROM website@server1

As this is a received email into your account, you would normally expect the TO field to be to yourself. In CASE 1, FROM is yourself and the TO field is yourself If the 'TO' is you then the 'TO' will be entered into the 'FROM' as it is you who is sending the email and email was received and currently resides in website@server1 mail account. 'Reply-TO' will be honoured because you would not want to 'Reply' to yourself.

In CASE 2, 'FROM' is from yourself, but the TO field is not you. 'FROM' will therefore be the default account or the mail account where the email is currently located. As the 'TO' field is not you, then the reply seems to be using the Original FROM field. Hence the following is directly copied into same fields. TO enquiries@server1 REPLY-TO enquirer@server2

It is as if you need to trick your mail account into believing the 'enquiries@server1' is also you.

Try this suggestion: For your mail account 'website@server1', create an additional 'identity' for email address 'enquiries@server1'.

• Right click on 'website@server1' mail account in Folder Pane and select 'Settings'.
• Account Settings window opens.
• Right side near bottom...click on 'Manage Identites'
• click on 'Add'
• Add the enquiries@server1 email address.
• when completed all details click on 'OK
• Click on 'OK

Good info here: https://support.mozilla.org/en-US/kb/using-identities

Then force to check all identities from self.

• 'Menu icon' > 'Options' > 'Options' > 'Advanced' > 'General' tab
• click on 'Config editor' button
• It will say to be careful :)
• In top search type : all_ident

This is the line you are looking for:

• mailnews.reply_to_self_check_all_ident

You need the value to say 'True'

• If it says 'False', double click on the line to toggle the value to 'True'
• Close window - top right X
• click on 'OK'

Exit Thunderbird. wait a few moments for background processes to complete. Start Thunderbird.

Perform tests and report back on results.

Thank you Toad - creating identities helps me avoid the errors in Scenario 1 Case 2.

When I create an identity (for the address which the server is forwarding) under the main account (to which it is being forwarded) Scenario 1 Case 2 now works as I would expect it to, that is, replies go TO the original REPLY-TO field, FROM the original TO field. I did not need to change mailnews.reply_to_self_check_all_ident from false to true.

Scenario 2 Case 2 still uses the default account as you confirmed, even if the original was TO one of my other accounts or identities.

It would make sense to me for Thunderbird to scan through the original TO, CC, and BCC fields for the first configured account address to use as the FROM address in the reply (and always honour the REPLY-TO field, never just copying it directly to a reply). This would avoid using the default account to reply to completely unrelated emails in Local folders (scenario 2 case 2). It would also avoid replies bouncing straight back at me (scenario 1 case 2).

I appreciate that using identies is a really neat way of having the reply come from the original TO address, but the other two cases are so unexpected I wonder if the suggestion in bold would be taken as a positive suggestion for improvement?

I am going to mark your solution as fixing the problem however, since I realise that checking recipient fields for other identities but not for other accounts is probably a well-established strategy for Thunderbird.