Here is how to reproduce the behavior on discourse 2.7.9:
- Create category A with mail firstname.lastname@example.org and category B with mail email@example.com
- Post a message in category A
- Reply via email and change the To: so that it is firstname.lastname@example.org
- The message ends up in category A, as a reply to the original message, instead of category B
This is presumably because the mail headers have information that allow discourse to know this mail was sent as a reply from the original message. So it has to make a choice: should this message be sent to:
- category B because of the To: field?
- category A because of the field that identifies it as a reply to a message in category A?
There probably are advantages to both. However, one could argue that landing the message in category B is the least surprising option for the user.
What do you think?
Edit Here is a use case where that could happen:
There was a meeting discussed in a topic in category A. Someone drafted the minutes of the meeting and started a reply via email as a followup to the topic in category A. But then, before sending the reply, they thought best to review the draft with only a few people to reduce the noise. So they changed the To: field to go to category B with less people involved. And they were surprised that the draft ended up in the original conversation in category A instead.