Spark Mail - Spark helps you take your inbox under control. Instantly see what’s important and quickly clean up the rest. Spark for Teams allows you to create, discuss, and share email with your colleagues
Nexmo - Nexmo is a simple two way SMS API with global reach and wholesale rates
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
MessageBird - Reach 7 billion phones in seconds via SMS, Chat & Voice. Try it for free and improve your communication.
K-9 Mail - K-9 is an opensource email client making it easy to chew through large volumes of email.
Plivo - Plivo simplifies your customer engagement.