Gmail Mail Merge - Send personalized emails with attachments
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
Dynamic Campaigns by Sigstr - Share the most relevant content in every email
HEY - Email at its best, new from Basecamp.
Dynamically Personalized Emails by QGraph - Hyper-personalized emails for E-commerce
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.