Last week, New York Times reporter Nick Bilton fessed up to having 46,315 unread emails in his inbox.

It's no secret that some of us are better than others when it comes to keeping on top of email. We've all seen email inboxes with 100, 500, even more than 1,000 unread emails--all silently screaming for attention and, in a cruel twist, driving the victim/recipient ever further into a vicious spiral of frozen inactivity (the more unread emails accumulate, the less we ever want to go near them).

Email implosion isn't always entirely the individual's fault. Truth is, any business can (but most don't) produce immediate, lasting productivity gains by agreeing on email protocols: in other words, simple rules for handling email.

Of all email protocols (such as: Don't use all caps; don't bcc unnecessarily; don't "reply all" unless you must), the biggest gains, and greatest ease of implementation, are in how you use email subject lines.

The Email Subject Line Dissected

I'm not referring to the need to make the text of the subject line meaningful (for example: "Agenda for Thursday's meeting attached" rather than "Re: Thursday"). Though the text of the subject line is important, there's another, more compelling issue at stake, and it's this: The key reason most people don't open and act on emails efficiently is because they're afraid of what they might find inside. You can use the email subject line to overcome that fear.

This may sound overstated, even dumb, but believe me, after years of counseling individuals and teams on productivity, I'm convinced that for most people, the volume of email is such that they can only give a relatively small amount of their energy to first opening, then parsing what has landed in their inbox.

Hence, the subject line carries the greatest impact on whether an email will actually get opened and acted upon. If you doubt that, as you check your inbox over the next day or so, monitor the impact an email's subject line has on whether, and how quickly, you open it--much less whether you actually do anything about it.

As a result, I've discovered that the single most effective way any business can increase email productivity is to agree on a series of short codes to use in email subject lines, to alert recipients as to what is expected of them.

The more a recipient can judge at a glance what the "resource impact" of an email is, the better he or she can act accordingly. Observationally, I've seen productivity improvements from 20 percent to 50 percent achieved by using this simple technique.

Here are the six subject line codes that I use, and benefit from, most. Feel free to copy and amend them as you wish. (Even better, make up your own, customized, relevant three-letter codes.)

[EOM]--End of Message

One of the biggest time wasters with email is the need to actually open the email to read the message. Although it might not seem much, repeated hundreds of times a week, it's quite a time burden--especially if you're working on a cell phone or other portable device.

If you can convey the entire message in less than, say, 60 characters, put the whole message in the subject line, and close the subject line with [EOM]. That way, your recipient knows everything he or she needs to know without even opening the email.

For example, this email with just a subject line and no body:

SUBJECT LINE: Weekly review is at 3 p.m. in Conference Room 3 [EOM] much better than the usual email that looks something like:

SUBJECT LINE: Weekly review meeting
BODY: This week's weekly review meeting will be held in Conference Room 3.

[NRR]--No Reply Required

A stronger version than the old standby FYI (For Your Information), NRR (No Reply Required) makes it explicit that you do not require a reply to this email.

Once someone can see--from the subject line--that there is no "response overhead" in reading the email, it's much more likely to get opened and acted upon. E.g.:

SUBJECT LINE: Agenda attached for weekly review [NRR]

[Y/N]--Yes/No Question

Most people can attack a yes/no decision with more alacrity than something more complicated or multifaceted. If you just need to know if someone wants chicken or fish, or whether 3 p.m. works better than 4 p.m., use [Y/N] to get your answer more quickly. E.g.:

SUBJECT LINE: Decision needed on location of weekly review [Y/N]
BODY: Do you want to meet at Starbucks or in the conference room?

[RB+ ]--Reply By (insert timeline)

Need a reply by tomorrow? Tell the recipient up front by putting [RB+1] in the subject line. A week from now = [RB+7], a month = [RB+30], etc. Need it today? [RB+0]. An hour from now? [RB+0.1]. E.g.:

SUBJECT LINE: Will you be attending the weekly review? [RB+2] [EOM]

[AB+ ]--Action By (insert timeline)

Works the same way as Reply By, except that this code alerts the recipient that there is an action embedded somewhere in the email that he or she needs to take by a certain date/time. E.g.:

SUBJECT LINE: I need the agenda for next week's weekly review [AB+5] [EOM]

These two codes together are incredible productivity promoters, as they can be used by the recipient to plan needed activities in advance.

[PYR]--Per Your Request

If you're sending someone something previously asked for (in other words, your email isn't initiating any new actions), let the person know right up front. E.g.:

SUBJECT LINE: Agenda attached for weekly review [PYR]

The bottom line: Don't wait until the weight of email "unreads" produces the inevitable dropped ball or missed deadline--or worse, the need for total email "amnesty." Establish and implement your own set of email subject-line protocols today.

Discover how to optimize communication within your organization. Download a free chapter from the author's WSJ bestseller Predictable Success: Getting Your Organization on the Growth Track--and Keeping It There. Learn more about building a world-class culture that will rapidly accelerate the growth of your business.