In many markets, email has become a more important customer interaction tool than the phone. And for many companies, most of the email sent out is not person-to-person: it's sent in bulk blasts. Email blasting tools and services are evolving at a very rapid pace, with the product definitions blurring (particularly when it comes to the marketing automation category). So let's try to get things straight.
This is the classic bulk email system that sends the same message out to a very wide range of people. If you're the sender, you may call it "lead nurturing." If you're on the receiving end, you may call it spam. Since the CAN SPAM law specifies hefty fines for unsolicited email (and common sense says "don't irritate your prospects and customers"), the first order of business is to make sure that the list you are mailing to has opted in.
Of course, the exact definition of "opting in" is a matter of noisy and endless debate. The core concept is that the recipient has expressed interest in the topic of your email. Fine, but what do you do when there's a new topic that nobody could ever have opted in to? The best strategy here is to put an opt-in appeal for the new topic in all your current email blasts (and of course, liberally sprinkle opt-in offers in your website).
This means, of course, that your CRM system will have to maintain a profile for all leads and contacts of all the horizontal blast topics they're interested in. The CRM system's built-in "opt out" flag should only be used for people who've said "never email me again." The topic interest profile must be a custom field shown as a multi-select pick list, so it doesn't consume too much screen real estate.
For a company of any size, it's critical to do a full two-way integration between the email blaster's "bounce" and "opt-out/interest" tables with the CRM's email address and topic profile fields. Unfortunately, this is only partly available off the shelf. Expect to write some triggers or data-translation code if you have to manage dozens of topics or product areas.
Success of horizontal email campaigns hinges on the quality of the list, and the relevance of the content. The interest tables takes care of relevance... but the quality of your mailing list is trickier. Most purchased lists have very poor yield: the best mailing list in the world is the one you already have. It's the one stored in your CRM system. So groom it and manage it well.
Vertical "drip emails"
Vertical email campaigns are fully automated as well, but they couldn't be a starker contrast to horizontal campaigns. Vertical campaigns are never done to huge groups the way horizontal blasts are. A vertical campaign starts in response to a user action, such as registering on a website or requesting a download. To work effectively, the vertical campaigns should be highly aligned with the specific area of the customer's interest and done in fairly rapid sequence. For example, the first drip email might be sent within a few hours of the prospect's action, followed by emails 2, 4, 6, and 10 days later. In contrast, horizontal blasts may be sent only on a monthly basis.