Messaging

LiveKit

Open-source realtime media infrastructure with the Agents framework, SIP, and phone numbers

• realtime
• voice-agents
• webrtc
• +3 more
• +2 more

Resend

Email API for developers with React Email, batch sending, and an official MCP server

• email
• transactional
• developer
• +2 more
• +1 more

Vapi

Voice agent platform handling telephony, turn-taking, interruptions, and warm transfers

• voice-agents
• telephony
• realtime
• +2 more
• +1 more

Knock

Notification infrastructure API — workflows, preferences, and multi-channel delivery for agent output

• notifications
• workflows
• multi-channel
• +1 more

Postmark

Transactional email with high deliverability and detailed delivery webhooks

• email
• transactional
• deliverability
• +1 more

Retell AI

Managed phone agents with conversation design, simulation testing, and production monitoring

• voice-agents
• telephony
• phone
• +2 more
• +1 more

SendGrid

Email delivery and marketing API by Twilio

• email
• marketing
• transactional
• +1 more

Twilio

SMS, voice, WhatsApp, and verification APIs, with an official MCP server over the platform

• sms
• voice
• whatsapp
• +3 more
• +2 more

Pusher

Hosted realtime channels and WebSocket delivery

• realtime
• websockets
• messaging
• +1 more