mettle/sendportal ? reverse-engineered prompt

Build me a self hosted email marketing app called SendPortal that I can run on my own server.

I want it to let me manage subscribers and lists, create and send email campaigns, track opens and clicks, and view simple reports so I can see how each newsletter performed. It should support multiple workspaces or domains, since I may want to separate different brands or clients. Also include user login and a clean admin area so people can manage everything in one place.

Please make it work with common email services like Amazon SES, Postmark, SendGrid, Mailgun, and Mailjet, and set it up so I can easily plug in my own provider settings. Use the project’s existing Laravel based structure and make it feel like a polished modern product. If anything is unclear, look up the current docs online and follow the recommended setup.