MailClark - The Slack bot for external communications
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
Alert.email - Get your important emails delivered to a Slack channel
PigeonBot - Send emails via Slack with the /email command
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
Helpwise - Shared inbox for your team email addresses