classes/Emails/Email/Headers.php
public function add(string $name, string $value): void
    {
        $header = $this->make();
        $header->name = $name;
        $header->value = $value;
        $this->set($header);
    }
public function add(string $name, string $value): void
    {
        $header = $this->make();
        $header->name = $name;
        $header->value = $value;
        $this->set($header);
    }
public function add ( string $ name , string $ value ) : void { $ header = $ this -> make ( ) ; $ header -> name = $ name ; $ header -> value = $ value ; $ this -> set ( $ header ) ; }
Add a custom header.

@param string $name The name of the custom header.
@param string $value The value of the custom header.
@throws \InvalidArgumentException
Add a custom header .