Opencart API for Mobile App Development

I'm in need of an experienced Opencart developer to build an API for my mobile application.

Key features of the API should include:
- User authentication and registration
- Data retrieval and storage
- Facilitating the sending of emails through the server itself

Ideal candidates should have:
- Robust experience in Opencart development
- A distinct understanding of API construction for mobile apps
- An ability to conduct comprehensive troubleshooting and fixing of potential bugs.

Experience with server-based email sending is a significant plus.