Hi Exchange Expert,
This morning I had an inbound mail issue. Outbound email was fine and working normal. There was intermittent inbound mail issue. No modification on exchange server configuration.
Error 421 service not available remote server has closed connection. Even when I tried to telnet from outside I got an error 421 4.3.2 service not available.
It started working after I adding 0.0.0.0 - 255.255.255.255 to receive connector -receive mail from remote servers list.
It was working fine until yesterday without specifying this IP range.