Hi, guys !
I got a problem with an Exchange mail server - it is located in a private LAN, behind a NAT device (Cisco 1712 - c1700-k9o3sy7-mz.123-7.T1.bin).
The problem I have is that I cannot connect using SMTP from outside - Outlook Express reports various errors.
After doing some investigations I found out:
- telnet on the real (private) IP address of the email server on port 25 works fine
- if I try it for the public IP address of the router which is translated for port 25 to the internal IP of the exchange server port 25, then I get the login banner from the Exchange server, but immediately after I type the first character in this session I get "Connection to host lost." .
I removed all access lists and the symptom persists. No CBAC configured.
The NAT statement is
ip nat inside source static tcp <internal IP> 25 <external IP> 25
Similar statement for POP3 on port 110 - and telnet works fine on tcp:110.
Does anyone have any ideea here ?
I would suspect a NAT configuration problem, like wrong timers or something related to the translation properties but I am really lost here.
Any suggestion would be appreciated.
Thanks
