Lehigh's Gmail system makes it easy as well: With the questionable message open, select the small 'down arrow' next to the 'reply' button. In the menu, choose 'Report Phishing'.
You can also use the Phish Alert Button locate on the right side of your email inbox. Simply select the questionable message and click the Phish Alert Button and confirm you want to send it. This will automatically send the message to the correct team to handle the investigation into the message.
This is the Phish Alert Button.
KnowBe4 Phishing Campaigns and Training