Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Recurrr - Send recurring emails
Fantastical 2 - Fantastical, the Mac calendar app you'll enjoy using. Quickly create new events with natural language input and more.
SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.
Morgen.so - All-in-one Calendar, Tasks & Scheduler. Morgen is the single hub for everything that revolves around time management.
FollowUpThen - The simplest way to schedule an email reminder