Probably the most commonly used medium for direct marketing is direct mail, in which marketing communications are sent to customers using the postal service. In many developed countries, direct mail represents such a significant amount of the total volume of mail that special rate classes have been established. In the United States and United Kingdom, for example, there are direct mail rates that enable marketers to send mail at rates that are substantially lower than regular first-class rates. In order to qualify for these rates, marketers must format and sort the mail in particular ways - which reduces the handling (and therefore costs) required by the postal service.

Direct mail permits the marketer to design marketing pieces in many different formats. Indeed, there is an entire subsector of the industry that produces specialized papers, printing, envelopes, and other materials for direct mail marketing. Some of the common formats, include:

• Catalogs: Multi-page, bound promotions, usually featuring a selection of products for sale.
• Self-mailers: Pieces usually created from a single sheet that has been printed and folded. For instance, a common practice is to print a page-length advertisement or promotion on one side of a sheet of paper. This is then folded in half or in thirds, with the promotional message to the inside. The two outside surfaces are then used for the address of the recipient and some "teaser" message designed to persuade the customer to open the piece.
• Poly-bag packages: Large (often 9x12 or bigger) full-color packages sealed in a clear plastic outer wrap. The contents show through the poly-bag, giving the potential for maximum initial impact. Poly-bag packages can be extremely effective, but also quite expensive.
• Postcards: Simple, two-sided pieces, with a promotional message on one side and the customer's address on the other.
• Envelope mailers: Mailings in which the marketing material is placed inside an envelope. This permits the marketer to include more than one insert. When more than one advertiser is included, this is often called "marriage mail".
• Snap Mailers: Mailers that fold and seal with pressure. The sides detach and the mailer is opened to reveal the message.
• Dimensional Mailers: Mailers that have some dimension to them, like a small box.
• Intelligent Documents: Programmable mail pieces built dynamically from database information, and printed digitally for faster production.

Advantages and Disadvantages of Direct Mail

Advantages include the following:

• Targeting - Historically, the most important aspect of direct mail was its ability to precisely target previous customers. If a suitable list was available, it also did a good job of targeting prospects.

• Personalization - Direct mail can address the customer personally and be tailored to their needs based on previous transactions and gathered data.

• Optimization - Because of its direct accountability, direct mail can be tested to find the best list; the best offer; the best timing (and many other factors). Then the winning tests can be rolled out to a wider audience for optimal results.

• Accumulation - Responses (and non-responses) can be added to the database, allowing future mailings to be better targeted.

Business-to-Business Mailings (B2B)

Business products and services have long used direct mail to promote themselves. Traditionally, this worked in one of two ways. As a direct sale, therefore precluding the use of a salesperson or a retail store, or as a method of generating leads for a salesforce. The former method was ideally used by products that were easy to sell, were familiar to the prospect and needed no demonstration. The latter method was used for large ticket items or for those that needed demonstration for example.

 Direct mail

Advertisers often call it "targeted mailing", as mail is usually sent out following database analysis. For example a person who likes golf may receive direct mail for golf related products or perhaps for goods and services that are appropriate for golfers. The USPS prefers to call it "advertising mail" (admail for short), noting that some people might find offers of interest to them in it.