Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
NeverBounce - Real-time email verification and cleaning to ensure emails never bounce.
MailClark - The Slack bot for external communications
Email List Verify - The Fastest Way to Improve Email List Deliverability and ROI
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
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.