Add Sendgrid integration (incoming email handling)

tests/units/ToolTest.php

@@ -0,0 +1,15 @@
+<?php
+
+require_once __DIR__.'/Base.php';
+
+use Core\Tool;
+
+class ToolTest extends Base
+{
+    public function testMailboxHash()
+    {
+        $this->assertEquals('test1', Tool::getMailboxHash('a+test1@localhost'));
+        $this->assertEquals('', Tool::getMailboxHash('test1@localhost'));
+        $this->assertEquals('', Tool::getMailboxHash('test1'));
+    }
+}