October\Rainlab\Support\Facade\Mail class is not found.

How can i solve this issue, i checked almost everything.

Need Help please!

Remove config.platform from your composer.json file. It should look something like this

"require": {
    "php": "^7.2",
    "october/rain": "dev-develop as 1.1",
    "october/system": "dev-develop",
    "october/backend": "dev-develop",
    "october/cms": "dev-develop",
    "laravel/framework": "~6.0"
},
"config": {
    "preferred-install": "dist"
},

Then perform composer update to fix it

Thank you for your answer, but now I'm getting this error: "Process could not be started [The system cannot find the path specified.]".