In this article, Bob Hale answers the question "What is the role of email and who should own it?". This is what he says:

Media should be grouped by primary objective. Because email is generally sent to elicit a response, it should be a part of the larger direct marketing program. When it's closely tied to the direct marketing arm of an organization, outgoing email can be managed as one part of a fully integrated initiative, including direct mail, telemarketing and other efforts.

Bottom line? Email can be a powerful marketing tool, but it needs to be held to similar communication and analytics standards as direct mail. As one more tool in the one-to-one marketing arsenal, email goals, timing and response data should be coordinated and aggregated with other parts of the plan.

By applying sophisticated analytics across all media, marketers can create and learn from more effective multichannel campaigns. Segregating email marketing from the direct marketing group can result in weaker campaign results, message inconsistency, lost time and the inability to maximize the overall budget.

Source: BtoBonline.com