According to RFC 2822 section 3.6.4, the In-Reply-To field of a message may contain multiple message IDs just like References. When it does, this indicates that the message is directly replying to multiple previous messages. I am in the process of creating an add-on which does exactly that, i.e., allows the user to reply to multiple previous messages in a single reply to all the senders of all the previous messages. I would therefore like to (correctly) populate In-Reply-To with the mesage IDs of all the messages being replied to. Unfortunately, Thunderbird makes this impossible. It does not provide any ability to set the In-Reply-To field as such before the message is handed off for transmission, and even if I hard-coded a special In-Reply-To field into the message header before it is sent, its contents would be forcefully overwritten by mime_generate_headers in nsMsgCompUtils.cpp. In short, Thunderbird's core code is preventing me from making my add-on standard-compliant. :-( While I understand the desire for Thunderbird to be "smart" and set In-Reply-To automatically when one isn't provided, it should also provide a way for the setting to be overridden, e.g., by allowing a value for this field to be specified in nsIMsgCompFields and to use the value there when it is specified.
Sounds like an enhancement to me. We'll accept a patch ;-)
Severity: normal → enhancement
You need to log in before you can comment on or make changes to this bug.