SendRecurring - SendRecurring allows you to setup, send, and maintain scheduled email reminders.

ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.

Recurrr - Send recurring emails

clearout.io - Clearout Email Finder & Email Verification Service - Drive sustainable business growth by expanding your reach, lowering hard bounces, and improving deliverability rates.

FollowUpThen - The simplest way to schedule an email reminder

DeBounce - Email Validation, Email Checker, Data Enrichment and Appending Tool. Using DeBounce remove invalid, disposable, spam-trap, syntax and deactivated emails.