The actual purchase of a mailing list along with the rights to mail it directly. Permission can only be “sold” if the subsequent mailings continue to match the frequency, brand name, content, and “from” of the past owner’s mailings — and even then this is a somewhat shaky procedure on the spam-front. You are in effect buying a publication, and not just a list.

Combining Email Marketing with Other Types of Marketing
Whether you choose to do your marketing online or offline, one thing does not change. This is the concept that no single marketing strategy will be as effective as a combination of two or more marketing strategies.