Update: I'm re-reading this in April 2023, twelve years later, and it's impressive how well this also applies to our modern chat-based communications channels. The Basic Principles never change, really.

Since being part of a larger company, I'm hearing people saying "we need a new mailing list for that" way too often.

People are afraid of busy mailing lists sometimes, but in terms of fostering open collaboration and communities a busy list is excellent.

Another problem is people writing 1-to-1 emails instead of writing to the list, as an attempt to avoid making the list even noisier. If your message is on-topic with a well written subject line, and as concise as possible, it's not noise and definitely belongs on the list.

Stefano's Mazzocchi briefly explains this in his ApacheCon 2006 slides titled all you wanted to know about Open Development community building but didn't know who to ask. I haven't found that pattern described in a more accessible way than among Stefano's 303 PDF slides so far, so here's a summary that I hope is faithful to the original idea.

The Busy List Pattern

Here's my summary of that part of Stefano's slides (starting at page 200 in his PDF file), with some additional comments of mine.

The pattern starts with somebody suggesting that the mailing list is too noisy and should be split in multiple ones.

Restaurants and night clubs, however, know that packed rooms help marketing…what's more boring than being alone in a restaurant?

But we're not a bar…we can't go on getting 200 messages on that list every day, can we?

Actually we can…if everybody who posts to the list is extra careful about how they post, a list with 200 or more messages per day is perfectly manageable - but only if the subject lines are very carefully chosen and evolved (see below), and only if people are very careful about what they post, to maximize clarity and avoid wasting other people's time.

We should strive to keep our lists as packed as possible. It's hard to set a limit, but before splitting a list you might ask if people are using it efficiently. First try to improve the signal to noise ratio, and if that really fails you might consider splitting the list.

If you really need to split the list, do it by audience and not by topic - a consistent audience will lead to an interesting list, whereas scattering topics all around makes cross-topic discussions painful.

Careful with those subject lines

The subject line of messages makes all the difference between a noisy list an a useful one.

Choose sensible subject lines that allow people do decide if they want to read your message or not.

Reread your subject line before sending - does it really express what your message is about, and does it contain any relevant call to action?

Change those subject lines when the thread changes topics.

Address one topic only per thread.

Use [MARKERS] in subject lines to tag messages.

Simple rules like this will boost your list's efficiency tremendously - there's more good stuff like this in Stefano's slides, make sure to have a look!

Update (8 years later...this is still as valid as ever!): my survival guide has more guidelines on how to cope with large mailing lists.