1. Boomerang for Gmail is a Firefox / Chrome plugin that lets you take control of when you send and receive email messages.

  2. FollowUp for email is a lightweight productivity suite that keeps your conversations and tasks from slipping through the cracks. Set perfectly timed reminders that arrive at the top of your inbox, right when you need them.

  3. Never-Forget.me is a delayed messaging service allowing you to compose email messages now which remain unsent as long as you click a link, at a recurring interval you specify, to continue to postpone the sending of your message

  4. Gmelius is a next-generation CRM and shared inbox for Gmail, tailored to the needs of SMEs that helps you sell more productively, organize and scale your pipeline, manage and build valuable customer relationships.

  5. Automatic follow up emails. Keeps on bumping until you get a reply.

  6. Sales Engagement platform with bunch of sales engagement tools like Email Tracking, Document Tracking, Mail Merge etc. to boost sales teams productivity.

  7. B

    Bumper is a stripped down version of FollowUpThen, followup.

  8. Laytr is the easiest way to defer emails.

  9. LetterMeLater.com allows you to send emails to anyone, with the ability to have them sent at any future date and time you choose.