Finally, you have to avoid the appearance of Spamming. There are three tests you can apply to find out. In fact, of all the commercial categories in the survey, travel was tops. Because air travel prices fluctuate dramatically, based on availability of seats. Books may be an ideal product for e-commerce, but their prices are more static and availability is not as much of a problem.
Time is the second test.
Many products are seriously dependent on new releases and seasonality. Software enthusiasts, for example, want to know when new software becomes available. Skiers may be interested in fall tune-ups and February trips to the Rockies. The product's dependence on information is the third factor. Make sure it's targeted to interested parties and completely voluntary.