Please review the link of the article Wrote by Microsoft Support person.. About How to send E-mail Campaign Automatically in CRM 3.0
When you distribute e-mail activities for a campaign by using Microsoft Dynamics CRM, the e-mail activities are not sent to the recipients automatically. You must open each e-mail activity and then send it manually. This article describes how to create a Workflow .NET assembly to send e-mail activities automatically.
Feel free to contact me, if you have any query.. email@example.com
Microsoft CRM Developer