Roundcube - Web-based IMAP email client
DiscoverOrg - DiscoverOrg is an IT sales intelligence platform providing technology marketers access to data, IT org charts, and real time projects.
HEY - Email at its best, new from Basecamp.
Clearbit - Clearbit provides Business Intelligence APIs
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
InsideView - InsideView aggregates and curates all the company and contact data, news and social insights, and professional connections you need to do business better.