Receiving HTTP request from single email but varying IP addresses?

Question

I have a server, and I was monitoring the incoming requests. There is a particular email, from which I'm getting multiple requests, but the IP address keeps changing little by little every few days. Example -

Request 1 -> (Email1, X.Y.Z.56)
Request 2 -> (Email1, X.Y.Z.56)
(after few days...)
Request 3 -> (Email1, X.Y.Z.57)
Request 4 -> (Email1, X.Y.Z.57)
(after few days...)
Request 5 -> (Email1, X.Y.Z.58)
Request 6 -> (Email1, X.Y.Z.58)
Request 7 -> (Email1, X.Y.Z.58)
(after few days...)
Request 8 -> (Email1, X.Y.Z.59)

How is the user able to change his public IP address so often? The requests are from the same email.

Answer 1

Got some help from my colleague. This is very interesting. Here is the complete discussion - Quora Link

It all depends on the ISP. It often allocates IP addresses dynamically, based on availability.