The process of joining a mailing list, either through an email command, by filling out a Web form, or offline by filling out a form or requesting to be added verbally. (If you accept verbal subscriptions, you should safeguard yourself by recording it and storing recordings along with time and date, in a retrievable format.)

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.