Sounds like a problem at the mail server. If the rules and DNAT is correct it isn't a firewall issue. I searched for the error and in 2 seconds I found it: Google esta tu amigo: Winsock Error 10053 ==== This problem occurs on servers which have had the Remote Access service (RAS) installed and later removed. This can be resolved by deleting rasphone.pbk file found in the Windows/System32/RAS directory. In addition to falling when accessed by the remote client, it would also die if you were using it locally and went to the ISP Logon Settings tab in the RAS dialog. ======= Or: Question/Problem: WSAECONNABORTED (10053) Software caused connection abort.
Answer/Solution: A connection abort was caused internal to your host machine. The software caused a connection abort because there is no space on the socket's queue and the socket cannot receive further connections.
WinSock description: The error can occur when the local network system aborts a connection. This would occur if WinSock aborts an established connection after data retransmission fails (receiver never acknowledges data sent on a datastream socket).
TCP/IP scenario: A connection will timeout if the local system doesn't receive an (ACK)nowledgement for data sent. It would also timeout if a (FIN)ish TCP packet is not ACK'd (and even if the FIN is ACK'd, it will eventually timeout if a FIN is not returned). ======
