Gravatar is a service for providing globally unique avatars and was created by Tom Preston-Werner. It is owned by Automattic, having integrated it into their WordPress.com blogging platform.
PHP: Hypertext Preprocessor is a server-side scripting language designed for Web development, but also used as a general-purpose programming language. PHP code may be embedded into HTML code, or it can be used in combination with various web template systems, web content management systems, and web frameworks.
Sarbacane is a complete email marketing & newsletter solution for creating, sending & analyzing campaigns, with a graphic editor for designing newsletters.
Gmail is a free, advertising-supported email service offered as part of Google's G Suite, with 15GB of storage, color-coded inbox filters and unsend button.
SendinBlue is an packed with powerful email management tools smart list segmentation, responsive email templates, campaign automation, and advanced reporting.