Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates
Chatlio - When you have a business to run, your average instant messaging software just will not do. You need an internal presence upon which your entire team can collaborate on. Read more about Chatlio.
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
slalert! - Get notified in Slack when your company/keyword is mentioned
MailClark - The Slack bot for external communications
Talkus - Chat with your website users from Slack