In a support discussion titled ‘We’re sorry, but your email message to didn’t work,’ tisawyer reports that emails CC’d to their Discourse community fail with an error: ‘Title has already been used.’ Stephen explains that Discourse treats emails without a topic-specific reply ID as attempts to create new topics — and since duplicate titles are not allowed, the system rejects them. He clarifies that Discourse does not recognize email threading via standard headers, because those are added during routing and not reliable for topic matching. Instead, Discourse relies on reply IDs embedded in the email address to link replies to existing topics. tisawyer acknowledges the explanation but wonders if Discourse could use email chain metadata to append replies to existing topics. Stephen reiterates that without the reply ID in the address, Discourse has no way to associate the message with an existing topic — emphasizing that inbound email replies must use the system-generated reply address to function correctly. This thread highlights a key limitation of Discourse’s email integration: it cannot auto-thread replies unless they include the unique reply ID, making CC-based workflows incompatible with topic continuity.
We started an email with our Discourse community CC’d. Subsequent reply all emails with Discourse CC’d received the email below. Is this expected behavior and if so why?
We’re sorry, but your email message to (titled Re: didn’t work.
Reason:
Title has already been used
If you can correct the problem, please try again.
If you aren’t responding to an email from discourse it will try to create a new topic with the same subject line. Duplicate topic titles aren’t allowed.
You can’t cc a discourse email address and have the replies appear in the same topic like that. Inbound email is for an individual to create or respond to a topic using reply-IDs.
Thank you for that reply. That explains exactly what happened. But I’m curious. I’m thinking there is some mechanism within the email headers that would indicate the reply is part of the same email “chain” (for lack of a better word)? Couldn’t Discourse recognize that and append the message to the topic?
That’s the purpose of the reply ID when you configure email replies.
If the topic-specific reply ID is missing from the address, then Discourse has no way to tell that the email relates to an existing topic.
Remember that when you send an email the header doesn’t exist, it’s created as the email is routed between systems and arrives on the target mail system.