Sortd - Rated the #1 App for Gmail
Brevo - Innovative online Email Marketing solution to manage your contacts, create & send your newsletters and track your results. More than 80 000 clients. Best prices and attractive features.
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
SendX.io - SendX (https://sendx.io) provides remarketing and retargeting tools for web businesses. You can use popups, landing pages, email, web push notification, automation workflows and FB / Google retargeting to drive more revenue.
KanbanMail - A Kanban board for your emails.
ConvertKit - Email marketing software for online creators. We help you earn a living online through an intuitive email marketing automation tool.