1423301 - 'Show in conversation' not listing responds to incoming mails

Status: RESOLVED INVALID

(Thunderbird :: Untriaged, defect)

Description

[fabian]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0
Build ID: 20171112125346

Steps to reproduce:

The 'Open in conversation' feature is working only, when a person sends me the first mail of a new conversation. By contrast, if I send the first message of a new conversation and recieve its response, the 'Open in conversation' feature only shows the current message.

This might be hoster related. How can my hoster fix the problem? What are the steps required in order to debug this problem? 

To reproduce:
- Tested in mail boxes with two different domains of the popular German hoster Hetzner.de
- Folder structure of Mailbox is as follows: INBOX, INBOX/Sent, INBOX/Trash
- Mailbox is clean
- Recieve a Mail from an arbitrary sender
- Respond to that Mail


Actual results:

- Respond icon is displayed next to the mail
- Mail with title "Re: ..." is successfully stored in INBOX/Sent
- Right click on the Mail in 'Inbox' -> 'Open in conversation' only shows the recieved message
- Right click on the Mail in 'Sent' -> 'Open in conversation' only shows the sent message


Expected results:

- 'Open in conversation' should show the complete conversation: recieved message + sent message