I am unable to receive external mail on my exchange server. I can send mail externally and between internal users but cannot received back from the outside world (like Yahoo mail, Gmail, Hotmail, and so on). Below are my set-up and configuration:

I used VM for all my Internal network set-up and configuration.

Host Server: Windows Server 2012 R2

1. Domain Controller: Windows Server 2012 r2----- IP Address: 10.0.1.4 (This server also server as my DHCP Server)

2. CAS and Hub Server: on Windows Server 2012 R2 (Exchange 2013 CU 8): IP Address: 10.0.1.8

3. Edge Server: on Windows Server 2012 R2 (Exchange 2013 CU 8) ---- 2 NICs

    Internal IP Address: 10.0.1.9 (on workgroup); External (Public) IP Address: 192.168.1.14

The following windows firewall port was open on the edge server:

Inbound traffic                                 Outbound traffic

SMTP tcp 25                                     Secure LDAP 50636 

DNS udp 53                                      SMTP tcp 25

DNS tcp 53

Edge Sync was configured successfully on the CAS Server.

4. Router -- A windows server 2012 r2 was configured as Network Address Translation (NAT) to bring internet access to my network. This machine is also a VM machine. 

    Public (External) IP Address: 192.168.1.13); Internal IP Address: 10.0.1.1 (This address is my internal Gateway IP Address)

5. I configure port forwarding (SMTP) to the internal IP Address of my edge server (i.e. 10.0.1.9)

For the purpose of this testing I bought a domain name and SAN Certificate for a year. Below is my Public DNS Configuration:

FQDS                                          DNS Record Type      Value 

DCK.co.uk                                   MX                           mail.dck.co.uk

mail.dck.co.uk                              A                              192.168.1.14

owa.dck.co.uk                              CNAME                     mail.dck.co.uk

autodiscover.dck.co.uk                  CNAME                     mail.dck.co.uk

Note: An A Host record was created for the Edge Server on the internal DNS with the internal IP Address.

Edge        A           10.0.1.9

I look forward to hear from you.

Thanks

Hi ,

is this issue is happening for all the users in exchange?

what is the last major change happened on your servers ? 

What is the NDR received on the sender end ?

Just check those messages are queued up on your smart host (i.e edge server ) ?

just do an inbound email test from EXRCA and share us the results ?

what would be the results for the test mail through telnet command from internet to your internal users ?

Hello

192.168.1.14 is not public.