Logowanie Gmail and other 86,400 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
This is the G-Mail login logo. There is a rectangle which contains an "M" that uses the left and right of the rectangle to form the left and right of the "M". There is an arrow through the top that points down.