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Odd behavior WRT "reply" ... sends to the "to address" , from the "from address" (ie does not swap)

  • 2 replies
  • 0 have this problem
  • Last reply by Graeme V

Graeme V
Graeme V

My name is graeme , my wife Olivia.

I have many many messages from various people; if I reply to a a mail from "fred", Thunderbird creates a mail:

to: fred@xxxx from: graeme@xxxx

I have several messages from my wife , that behave in this same fashion (ie , as you would expect) but ONE message, when I reply the message displayed in Thunderbird (ie NOT YET SENT, so no SMTP etc yet involved) says:

(it does NOT have a REPLY-TO header BTW)

to: graeme@... from olivia@.....

...I've search back though my mailbox and all the mails from my wife work as you would expect, bar this one ...AND ONE OTHER that I found:

This says:

from olivia@.xxxx to: company@xxxx, olivia@xxxx. graeme@xxxxx

When I hit reply , it generates a message:

from olivia@xxxx to: company@xxxx, olivia@xxxx. graeme@xxxxx

So the from and to in the reply are exactly the same as the from/to in the initial message (they are not swapped)


So, to be clear 99% of messages are fine, it's just one or two cases where I get this odd behavior.

My name is '''graeme''' , my wife '''Olivia'''. I have many many messages from various people; if I reply to a a mail from "'''fred'''", Thunderbird creates a mail: to: '''fred'''@xxxx from: '''graeme'''@xxxx I have several messages from my wife , that behave in this same fashion (ie , as you would expect) but ONE message, when I reply the message displayed in Thunderbird (ie NOT YET SENT, so no SMTP etc yet involved) says: (it does NOT have a REPLY-TO header BTW) to: graeme@... from olivia@..... ...I've search back though my mailbox and all the mails from my wife work as you would expect, bar this one ...AND ONE OTHER that I found: This says: from '''olivia'''@.xxxx to: '''company'''@xxxx, olivia@xxxx. graeme@xxxxx When I hit reply , it generates a message: from '''olivia'''@xxxx to: '''company'''@xxxx, olivia@xxxx. graeme@xxxxx So the '''from''' and '''to''' in the reply are exactly the same as the from/to in the initial message (they are not swapped) So, to be clear 99% of messages are fine, it's just one or two cases where I get this odd behavior.

Chosen solution

Using the File -> "Open Saved Message" I was able to debug this situation.

I created two files:

mail-hand-crafted-FAILS.eml mail-hand-crafted-WORKS.eml

TL;DR:

The from address matches the email address of another account setup up with Thunderbird.

Long version:

The two emails (body) contains a description of the problem. I was unaware that Thunderbird ever did this matching up of email addresses. I always use the form graeme.somesuffix@xxxxx which is not (normally) recorded as an "account" in Thunderbird. I just make these names up to deal with sites that track email addresses. I guess many folks use name+suffix@xxxx form as sites like gmail.com discard this suffix when routing.

This might explain why the K9 developers are so worried about supporting this complex behaviour in their Android version of Thunderbird. 


   $ cat mail-hand-crafted-FAILS.eml 
   Date: Sun, 1 Feb 2026 19:31:30 +0000
   Subject: Re: Draft email to ACME 20260201
   From: The Sender <olivia.suffixfree@xxxxxxxxxx.com>
   To: The Receiver <receiver@xxxxxxxxxx.com>

   This email FAILS (meaning it exhibits the SPECIAL-BEHAVIOUR)

   SPECIAL-BEHAVIOUR being defined as:

   Hitting "Reply" generates an email where to & from are not reversed, so you end up
   sending an email to yourself!



   This email displays as:   From: The Sender <olivia.suffixfree@xxxxxxxxxx.com>         to: The Receiver <receiver@xxxxxxxxxx.com>

   If you hit reply it goes  From: Olivia Xxxxxxxxxx <olivia.suffixfree@xxxxxxxxxx.com>  to: The Receiver <receiver@xxxxxxxxxx.com>

   You'll note it changed "The Sender" to "Olivia Xxxxxxxxxx" this is (I assume) because I have an account setup with this Thunderbird
   with the name "Olivia Xxxxxxxxxx" and the userid olivia@xxxxxxxxxx.com , but the email address olivia.suffixfree@xxxxxxxxxx.com




   $ cat mail-hand-crafted-WORKS.eml 
   Date: Sun, 1 Feb 2026 19:31:30 +0000
   Subject: Re: Draft email to ACME 20260201
   From: The Sender <olivia.suffix@xxxxxxxxxx.com>
   To: The Receiver <receiver@xxxxxxxxxx.com>

   This email displays as:   From: Olivia Xxxxxxxxxx_with_suffix       To: The Receiver <receiver@xxxxxxxxxx.com>

   If you hit reply it goes  From: graeme xxxxxxxxxx <graeme@xxxxxxxxxx.com>  To: The Sender <olivia.suffix@xxxxxxxxxx.com>

   You'll note it does NOT say it was from "The Sender" is says "Olivia Xxxxxxxxxx_with_suffix" (and only that , no email address)
   The reply uses the From information on original (ie "The Sender") ... but for reply, it uses My From address

   FYI: I have an entry in the Thunderbird addressbook  Displayname="Olivia Xxxxxxxxxx_with_suffix"  email=olivia.suffix@xxxxxxxxxx.com
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All Replies (2)

Graeme V
Graeme V Question owner

BTW, another useful bit of info. When I quit this reply msg (without making any changes ) Thunderbird says "This message has been modified , discard, save, cancel) ... if I reply to a normal message and quit in the same fashion, it says nothing and just exits.

Graeme V
Graeme V Question owner

Chosen Solution

Using the File -> "Open Saved Message" I was able to debug this situation.

I created two files:

mail-hand-crafted-FAILS.eml mail-hand-crafted-WORKS.eml

TL;DR:

The from address matches the email address of another account setup up with Thunderbird.

Long version:

The two emails (body) contains a description of the problem. I was unaware that Thunderbird ever did this matching up of email addresses. I always use the form graeme.somesuffix@xxxxx which is not (normally) recorded as an "account" in Thunderbird. I just make these names up to deal with sites that track email addresses. I guess many folks use name+suffix@xxxx form as sites like gmail.com discard this suffix when routing.

This might explain why the K9 developers are so worried about supporting this complex behaviour in their Android version of Thunderbird. 


   $ cat mail-hand-crafted-FAILS.eml 
   Date: Sun, 1 Feb 2026 19:31:30 +0000
   Subject: Re: Draft email to ACME 20260201
   From: The Sender <olivia.suffixfree@xxxxxxxxxx.com>
   To: The Receiver <receiver@xxxxxxxxxx.com>

   This email FAILS (meaning it exhibits the SPECIAL-BEHAVIOUR)

   SPECIAL-BEHAVIOUR being defined as:

   Hitting "Reply" generates an email where to & from are not reversed, so you end up
   sending an email to yourself!



   This email displays as:   From: The Sender <olivia.suffixfree@xxxxxxxxxx.com>         to: The Receiver <receiver@xxxxxxxxxx.com>

   If you hit reply it goes  From: Olivia Xxxxxxxxxx <olivia.suffixfree@xxxxxxxxxx.com>  to: The Receiver <receiver@xxxxxxxxxx.com>

   You'll note it changed "The Sender" to "Olivia Xxxxxxxxxx" this is (I assume) because I have an account setup with this Thunderbird
   with the name "Olivia Xxxxxxxxxx" and the userid olivia@xxxxxxxxxx.com , but the email address olivia.suffixfree@xxxxxxxxxx.com




   $ cat mail-hand-crafted-WORKS.eml 
   Date: Sun, 1 Feb 2026 19:31:30 +0000
   Subject: Re: Draft email to ACME 20260201
   From: The Sender <olivia.suffix@xxxxxxxxxx.com>
   To: The Receiver <receiver@xxxxxxxxxx.com>

   This email displays as:   From: Olivia Xxxxxxxxxx_with_suffix       To: The Receiver <receiver@xxxxxxxxxx.com>

   If you hit reply it goes  From: graeme xxxxxxxxxx <graeme@xxxxxxxxxx.com>  To: The Sender <olivia.suffix@xxxxxxxxxx.com>

   You'll note it does NOT say it was from "The Sender" is says "Olivia Xxxxxxxxxx_with_suffix" (and only that , no email address)
   The reply uses the From information on original (ie "The Sender") ... but for reply, it uses My From address

   FYI: I have an entry in the Thunderbird addressbook  Displayname="Olivia Xxxxxxxxxx_with_suffix"  email=olivia.suffix@xxxxxxxxxx.com
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