Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.

Beeceptor - Unblock yourself from API dependencies, and build & integrate with APIs fast. Beeceptor helps you build a mock Rest API in a few seconds.

Freshdesk - Freshdesk is a cloud-based customer support software that lets you support customers through traditional channels like phone and email, social channels like Facebook and Twitter, and your own branded community

MockServer - Easy mocking of any system you integrate with via HTTP or HTTPS.

Zoho Desk - Industry's first context-aware Helpdesk Software

Webhook.site - Instantly generate a free, unique URL and email address to test, inspect, and automate (with a visual workflow editor and scripts) incoming HTTP requests and emails.