Email Threading

Thread \Thread\ (thr[e^]d), n.
4. (Fig.) Something continued in a long course or tenor; a
recurrent theme or related sequence of events in a larger
story; as the thread of a story, or of life, or of a
discourse. –Bp. Burnet.
[1913 Webster]

The above dictionary definition describes an Email thread very accurately. Consider the following scenario:-
Suppose Bob sends an Email to Alice asking her how the weather is in Chicago. The Email might take the following form:-

From: Bob <bob@foo.com>
To: Alice <alice@bar.com>
Message-ID: <00e201c5e8a0$ebf57510$45002c0a@foo.com>
Subject: How’s the weather in Chicago

Regards
Bob

Bob might not even be aware of all the information he has passed to Alice. For example his message is assigned a unique “Message-ID”, Bob doesn’t have to provide one, it’s taken care of for him. When Alice receives Bob’s Email, she might reply to it by sending Bob a new Email which would look something like this:-

From: Alice <alice@bar.com>
To: Bob <bob@foo.com>
Message-ID: <000a01c5e712$5b2c61b0$1a14ff3e@bar.com>
Subject: Weather

Hi Bob,
The weather is sunny and dry.
Love
Alice

For two people communicating directly with each other, this just about works as both parties know the topic being discussed. Now consider that Bob actually shares his Email with his wife and children. Bob sent the email, but his wife receives Alice’s response. She really has no idea why Alice is sending this information; it’s raining outside her house but Alice says it’s sunny and dry. She checks her Sent-Items and there are no messages with a subject of ‘Weather’ to indicate this is a reply. Bob’s wife shrugs and deletes the email from Alice as nonsense.

Imagine the problem if Bob shared his Email with hundreds of people and it becomes obvious that this method of emailing is unworkable. A shared Email box like this with hundreds or even thousands of people reading and posting is exactly how a Mailing List works.

Based on this, lets go back to Alice’s reply to Bob and do things a little differently. Firstly lets assume that Alice knows how to reply to Bob. Her response would then look something like this:-

From: Alice <alice@bar.com>
To: Bob <bob@foo.com>
Message-ID: <000a01c5e712$5b2c61b0$1a14ff3e@bar.com>
References: <00e201c5e8a0$ebf57510$45002c0a@foo.com>
In-Reply-To: <00e201c5e8a0$ebf57510$45002c0a@foo.com>
Subject: Re: How’s the weather in Chicago

Hi Bob,
The weather is sunny and dry.
Love
Alice

Now if Bob’s wife was to receive this email, it makes much more sense to her. Firstly, because Alice has used her Reply-To button, her Email client has inserted the References and In-Reply-To headers. This is called ‘threading’ and without it a mailing list rapidly becomes an unreadable mess.

In addition to threading her message, Alice has included the subject matter in the body of her reply preceeded with a ‘> ‘. This is a unversal convention to indicate quoted content from a previous message in the thread. Most Email clients will insert it automatically when replying. Alice doesn’t need to quote all of Bob’s message, (it could be hundreds of lines long), she just needs to quote the relevent part she is responding to. No matter who receives and reads Alice’s Email, it will make sense to them and be in the proper context in terms of the overall thread.

Do and Do not
Do thread messages. Use a Reply-To option when responding to an Email.
Do quote relevent text from the message you are responding to.
Do not quote all the text from the message you are replying to unless it’s all relevent.
Do type your text under the relevent text you are replying about.
Do not use a Reply-To option when beginning a new thread or topic.

And finally:
Do check your Email client properly inserts References and In-Reply-To headers. If it doesn’t, then select a different one that isn’t broken. There are plenty of good free ones out there.

Follow all these Do’s and Don’ts and your recipients will treat your input with higher regard. After all, if you can’t post the message properly, why should they expect your content to be of better quality?