Monday, February 05, 2007


Email subject lines

A little while ago, Microsoft blogger Raymond Chen suggested that you should use a subject line that's meaningful to the recipient when you write email. I strongly agree, and have more to say about that here. I also like Raymond's blog a lot, and want to link to it here. So I have.

My first comment is that you should use a subject line that's meaningful to everyone — to all recipients, if there are more than one, including everyone on the CC list, and to you, the sender. My favourite example in Raymond's list (because I've gotten these too) is “URGENT URGENT URGENT”. Remember that the recipient(s) will lose this in the mess, assuming it gets through their spam filters (see below). But remember also that if they do manage to respond, their responses will have a subject of “Re: URGENT URGENT URGENT”, and that won't be meaningful to you, either.

This is especially true for meeting invitations. At the office, it's common for executives to have their administrative assistants manage their calendars. The assistant will set up a meeting with me, and will send me an invitation on our group calendar system. The invitation will often have a subject like, “Meet with Barry.” That may be fine when it's on the executive's calendar, but it doesn't do much good when I accept the invitation and it's added to my calendar that way. Better would be “Meeting, Ellen and Barry.” Better still, “Discuss antispam project, Ellen and Barry.”

Do not ever, ever, ever leave the subject blank. Some systems will send the message with an empty subject. Some will fill in "No subject". Either way, it's not useful and is very likely to get your message eaten by spam filters. Even for social mail, fill in a sensible subject.

A friend recently asked me, “What does 'Kein Betreff' mean?” Ha. It's German for... “No subject”, of course. And my friend was wondering what the correspondent was asking, and thought the subject was significant.

Now that you're filling in a subject, don't just put noise in there. I have a friend who likes to use “from Barbara”. I know who it's from; the email already tells me that. Also, that's another incantation that's likely to run afoul of the spam filters. Try to put something there that says something about the content of the message, even for social mail. If you're talking about a restaurant you went to, put the name of the restaurant, or something about the food you ate. “I love salmon!” is a much better subject line than “Saturday” (but even the latter is better than nothing at all).

For business mail, this is critical. The more information you can put succinctly into the subject the better (but avoid being over-long; more than 40 or 50 characters isn't useful either). “A question” isn't useful. “A question about DKIM” is better. “A question about DKIM canonicalization” is even better. Intelligible abbreviations are fine, to keep it short. But the point is that when I'm looking through my inbox, I want to be able to identify the messages there, find which one I'm looking for, know which one I want to take action on.

Remember that spam is a huge problem and that some spam filters are quite strict. Avoid things that make your messages look spammier than necessary. Of course, anything can be mis-classified, and modern antispam software considers much more than just the subject, but there are some things in the subject line that are red flags and you can probably figure out what they are. Blank subjects. “Hi!” “Help!” “Urgent!” Things like that. Also, strings of exclamation points (“!!!!!”) or question marks (“?????”) are suspicious. Avoid them; they don't help the recipient, and they only make the subject line longer for no good reason.

In general, keep in mind that you might get only three messages a day and not care what the subject lines say, but that your recipients might get dozens or even hundreds of messages a day and be lost without sensible subject lines.


Anonymous said...

It’s also helpful to change the subject once a while to make it more relevant. Sometimes I see the same email being tossed back and forth, and the subject we are discussing right now is no longer the same one as 10 emails ago, but the subject line remains the same. It will cause a little problem if I need to read just one of them a week later.

Barry Leiba said...

That's a good point, and knowing when to change the subject line — and when not to — is a skill.

If you change the subject line too often, it can screw up "threading", the ability for email programs to collect the items in a particular discussion thread into one batch.

But if you don't change the subject when the discussion really has morphed into a separate one, you get confused in the way An points out.

I try to make a judgement about whether the discussion is just straying, but is still basically the same discussion... or whether it really has turned into a new discussion, and deserves its own thread.

Richard said...

I believe the reason people don't put meaningful subject lines is because the have nothing meaningful to communicate. They are just going through the motions, following the bureaucratic maxim, "look busy, do nothing."

My favourite subject line is: re: re:

Anonymous said...

Better than "A question about DKIM canonicalization" would be "DKIM canonicalization question". Some of us have multiple columns in our Outlook view and don't see more than a few words of the subject.

Anonymous said...

Regarding changing the subject: That's not the only thing that MUAs use to decide how to group messages into threads. Correctly-written MUAs use the In-Reply-To: and References: headers (which contain message IDs) to decide where to put a particular message; if you change the subject but don't fix those headers, your message will show up in the same thread in any MUA that handles those headers properly.

(And I doubt that includes Outlook, but then I'm not even sure whether Outlook *can* do a thread view.)

If the discussion has morphed enough to become its own thread, I usually use the "new message" button instead of the "reply" button, fill in the address, and paste in the stuff that I'm quoting manually. This is only because my mailer (Thunderbird) doesn't have any way that I can find to remove the References: and In-Reply-To: headers -- but then, it doesn't happen very often either, so it's not very annoying.

Anonymous said...

What I wonder is why HR-related emails always have a subject line of "John Doe", followed by a body telling us that John Doe has left to pursue other endeavors, John Doe has been promoted, or John Doe has just died.

boxmonkey said...

My first boss was the worst offender. I would get several emails from him every day with no subject. Then he'd ask me to do something that required going back and finding a message he'd sent me several days before that.

Yuri Khan said...

Better than “A question about DKIM canonicalization” and “DKIM canonicalization question” would be “DKIM canonicalization”. Because only the initial message is a question, but the subject will be inherited by all messages in the thread, which may or may not be questions.

Barry Leiba said...

«Regarding changing the subject: That's not the only thing that MUAs use to decide how to group messages into threads. Correctly-written MUAs use the In-Reply-To: and References: headers»

Indeed, but (1) not all clients use them in their threading (though most that do threading do), and (2) not all clients generate them, which is more of a problem... and that's why even clients that use them to thread have to fall back to using the subject lines anyway. It's all a mess, and it would have been better if these headers had been standardized properly.

I think (though I haven't explicitly tested this) that gmail will put all notes with the same subject into the same thread, without regard to the In-Reply-To and References headers.

Outlook certainly does a thread view, but it doesn't do it very well. If I remember correctly, it only uses one of the threading headers, and doesn't fall back to the subject lines when the threading headers are absent. Which makes for odd breaks in the threads.