By Alan Sharpe
Business-to-business direct mail marketers have learned through testing that a letter in an envelope usually generates more sales and pulls more inquiries than a self-mailer will. Usually. 
Self-mailers are still effective at selling products and services and generating leads, particularly in the following cases:
* seminar invitations
* event announcements
* trade show booth traffic generation
* software upgrade offers
* mailings to prospects who do not have a mailroom screen their mail (barbershops and factory foremen, for example)
* mailings where you want the prospect to pass along the mailing to colleagues
ADVANTAGES OF SELF-MAILERS
1. Cost: The primary advantage of self-mailers is their lower cost. Because they mail on their own, they are cheaper to print, are easier to assemble (no need to match addressee on letter with envelope with reply card), and require less handling (no envelope and lettershop inserting costs).
2. Simplicity: Self-mailers are usually easier to design. A graphic artist does not have to design a mailing envelope, letter and brochure, but instead designs one sheet of paper front and back.
3. Space: Self-mailers are a cost-effective way to present a lot of product photos, graphs, charts and other images.
4. Flexibility: Self-mailers can be as simple as a sheet of stock folded in half or as complicated as a large sheet of stock folded in ingenious ways, with tear off coupon, order form and pre-formed business reply envelope all in one.
DISADVANTAGES OF SELF-MAILERS
1. Performance: They hardly ever outpull the same information enclosed in an envelope.
2. Appearance: Self-mailers also yell “promotional message inside.” They are, by their very function, promotional. No one sends a personal message to friends in a self-mailer.
3. Tone: Self-mailers look less personal than envelopes do. And when you are writing to businesspeople, you want your correspondence to be peer-to-peer, not vendor-to-customer.
These are some of the reasons that self-mailers perform poorly compared with envelope mailings. Particularly in business-to-business lead generation, you want your direct mail piece to be perceived as professional and personal. If you are mailing to prospects in the C-suite (chief executive officer, chief financial officer), a letter in an envelope is the method that has proven most effective over the years.
So how do you decide if a self-mailer is better than a letter and an envelope? You test. Create a cost-efficient format, find a good printer, and test the self-mailer against a standard envelope mailing. If you are doing a first-time mailing for a new product or service, I’d go with an envelope, letter, brochure and reply card first. Then test a self-mailer against it later.
— Alan Sharpe is president of Sharpe Copy, Inc. (www.sharpecopy.com), a B2B direct mail copywriting firm.