As some of you might know, I am setting up an exchange server.
Now I ran into another problem:
I cannot connect to the SMTP service from outside the server!
The ports are opened in the gateway device (a ZyXEL USG50), Windows firewall is off.
I see the packets travekl through the ZyXEL firewall, and I can also see the packets with wireshark on the server, so I know they are getting all the way in to the server.
I also know it receives them, and sends out the reply - and this is where things go bad!
Analyzing with wireshark, I get these errors in the return packets:
Header checksum: 0x0000 [incorrect, should be 0x0779 (may be caused by "IP checksum offload"?)]
Acknowledgment Number: 0x8e3337d1 [should be 0x00000000 because ACK flag is not set]
What the (sorry my French) hell is going on?
I really cant figure it out..
Thanks in advance.