SendX.io - SendX (https://sendx.io) provides remarketing and retargeting tools for web businesses. You can use popups, landing pages, email, web push notification, automation workflows and FB / Google retargeting to drive more revenue.
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
Nova Inbox - Personalize emails in seconds, right from your inbox
HEY - Email at its best, new from Basecamp.
Mailblast - Email marketing on a budget using Amazon SES
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.