This service is especially useful if you immediately want to proceed to mass marketing, which is the case for most postcards, brochures, and flyers. To spare you the hassle of adding an address to each and sending the print products out by mail, your local and online printers can do the direct mailing for you. This will, of course, entail a certain amount to cover the expense of printing the address and mailing, but it does help you save on time, plus a part of your expense.
Look for a commercial printer that can offer you these services or those services that your printing project would require. A good and comprehensive list of ancillary services suggests that the commercial printing company values customer satisfaction and can be flexible enough to accommodate your needs.