> The actual code powering Gmail probably dates back to the late 80s or early 90s and has had several hundred thousands of hours of work put into it.

no. google did not exist until the late 90s.

various forms of internet email sure did, but most popular mtas of the google era shared very little code with predecessors from the 80s and early 90s (maybe sendmail) and google almost certainly wrote their own from scratch.

but your first point. that an archive browser that looks like gmail is not equivalent to a full tilt email service backend is valid.