Mailwasher - Over 8 million people use MailWasher as their spam filter
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird
Live Chat by Sumo.com - Instantly communicate with customers, prospects & visitors
Spam Reader - Spam Reader is a free anti-spam add-on for Microsoft Outlook.
Drift - A messaging app that helps you grow your business.