How does routing work?

Question

Ping

I can't access a mailer that is on a different subnet from my computer on the local network.
Routes are registered in the routing table.
There is access to my computer from the remote (in the opposite direction) network, but not back.
What can be wrong?

Answer 1

in NAT, in the firewall, in the absence of the desired route on the router.

Answer 2

https://linkmeup.ru/blog/14.html