where is my email?
Email doesn't just go from point A to point B.  It hops along a network path between nodes.

Some of these nodes (routers) will just forward the network traffic to the next node.

Some of the nodes (email servers) will store the email in a queue for dissemination to the next hop.

It is impossible to predict the length of time an email will take to get from point A to point B as there are too many unknown variables