Rory Sutherland Totally Mailed It

Mail simply does things that no other medium can do. There is a current fashion to try to use digital channels as a Swiss Army Knife. But the thing about Swiss Army Knives is that, unless you have nothing else to hand, they really aren't very good. And that's because, for every function they perform, there is a stand-alone implement which does the job better. If you need someone to commit to something, rather than simply feel something, nothing else comes close to mail. Moreover, if you want something to feel exclusive, or the recipient to feel special, nothing else does the job nearly as well. 
 

“Direct mail done well converts attention to action at perhaps 10-100x the rate of any other medium.”

It is very, very different to all other advertising media. As such, used on its own, it does things other media cannot do; but used in combination, it complements them magnificently. Having said all that, prepare to be surprised, direct mail done well converts attention to action at perhaps 10-100x the rate of any other medium.

There is a kind of trust and sincerity in the price of a stamp. You are putting your money where your mouth is and in an age of intangibles, anything physical is reassuring.
 

“The reason mail also feels so personal is primarily - it has your name on it.”

The reason mail also feels so personal is primarily - it has your name on it. It is clearly perceived as sufficiently expensive for the recipient to assume they have been chosen specifically to receive the message. You can send people stuff too. Actual things. Things they keep. At the very least, it can be put in a toast-rack for later perusal. You put it somewhere. And, even if you bin it, you have to decide to bin it and recycle it.

Consider the difference between seeing a job advertised in a publication and receiving a letter inviting you to apply. It's a very different emotional response, no? I think this makes my point. 

But there’s a creative reason too. It is one of the few remaining media which talks to people one-on-one in a conversational style. Long copy press advertising used to do this, but no one seems to be able to write it anymore. The direct mail industry still harbours writers who can write more than 12 words, and where the writer reveals something of their own personality in the content. This establishes a personal connection in a way only very skilled salesmen can match.

If you have a known prospect pool, or a clearly defined and addressable audience, your job is to establish a profitable relationship over time with as many of those people as you can. That is "How Brands Grow". Yes, direct mail is an expensive first date, but if you have the prospect of a lifelong relationship, why would you skimp on a first date?

“Even when your direct mail works brilliantly, your penny-pinching, digitally-fixated competitors won't copy you.”
 

I remember one particularly potent example of mail driving action - I had to write to about 20,000 people effectively asking them to do the client a small favour. It got a response rate of over 100%. Some recipients even passed the request on to others. But the real competitive advantage of direct mail is that - because it is effective rather than efficient - even when your direct mail works brilliantly, your penny-pinching, digitally-fixated competitors won't copy you.

If you’re thinking about using mail, first of all, find someone who can do it well. Or, failing that, find someone who you can be sure won't do it badly. God is in the details in direct mail, and it requires a very specific set of skills, as Liam Neeson might say. The wrong targeting, the wrong timing, the wrong call to action, the wrong proposition, the wrong creative approach - even the wrong opening sentence - can reduce the effectiveness considerably. And these things multiply. For these reasons, you must be prepared to test several approaches - and continue to test and refine them. Do not expect to hit the motherlode on your first outing.

At this point, if I am not careful, I will go off into a long discursion on the biological concept of costly signalling. But there is an appropriate level of cost and effort to certain forms of persuasion. You wouldn't take a first-date to McDonald's, and you wouldn't buy a Ferrari from someone who indifferently pointed to a few features and then wandered off.

Most advertising tries to get a customer to care about a business. Direct mail shows to a customer that a business cares about them. It really is as simple as that.