I notice that in Thunderbird, when I respond to a message, it puts a
little arrow in the subject which tells me that I've replied to the
message. If I look at my Inbox using webmail (Horde to be exact), I see
that I replied to the message. How does it know? I looked at the
headers, and I don't see anything about the fact that it has been
replied to.

In addition, I find that there is no easy way to find the email that
which is the reply to this message. I know it's in my Sent mail folder,
but is there any link between the two? If I move the mail out of my
Sent mail, what's the best way to find the reply in the future?

ben@peikes.com wrote:
> I notice that in Thunderbird, when I respond to a message, it puts a
> little arrow in the subject which tells me that I've replied to the
> message. If I look at my Inbox using webmail (Horde to be exact), I see
> that I replied to the message. How does it know? I looked at the
> headers, and I don't see anything about the fact that it has been
> replied to.

It's done with the IMAP \Answered flag. Flags are message
meta-information managed by the IMAP server. More on IMAP flags:

http://tools.ietf.org/html/3501#section-2.3.2

> In addition, I find that there is no easy way to find the email that
> which is the reply to this message. I know it's in my Sent mail folder,
> but is there any link between the two?

If you're using a decent MUA, the In-Reply-To: header field of the reply
will match the Message-ID: header field of the original message.

http://tools.ietf.org/html/2822#section-3.6.4

> If I move the mail out of my
> Sent mail, what's the best way to find the reply in the future?

I've gotten into the habit of having Thunderbird save my sent messages
to INBOX, that way get to archive whole threads (including my replies)
to the same (correct) place.


Bob

bedank.

bedank.