error with the Outlook Express and iptables with the nat and packet filtering

Hi friends, i has a big problem with the iptables and you rules, i want to doing a nat with the packet filtering but when i try access to my mail with the Outlokk Express I can't send and recived, the OE ask me a login and password, and show the following error

There was a problem logging onto your mail server. Your Password was rejected. Account: 'mail.gecyt.cu', Server: 'mail.gecyt.cu', Protocol: POP3, Server Response: '-ERR your network does not have access to this account', Port: 110, Secure(SSL): No, Server Error: 0x800CCC90, Error Number: 0x800CCC92

waht it is the problem someone can i help.
thanks very mouch.
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If the OE client receives this error then the communication through the firewall/NAT is working properly, since it is able to get the request to the server, and receive a reply from it. The actual text of the error ('your network does not have access to this account') makes me suspect a cause. My suspicion is this (cheating, in that I looked at the rules in your next post :^):
You DNAT the packets to forward them to the server. You SNAT them as well, so that they return to your firewall for reverse handling. The IP address of the firewall box (the one that the SNAT is putting in as the source IP on the requests) is not recognized as part of the appropriate IP range that the user account is expected to connect from, and the server is refusing to allow it. Quite a few ISP's do this now on SMTP, as an anti-spam measure, I've rarely seen it for POP3 though.

Is this an email server that you control? If so, or if you can influence someone who can, check the configuration to see if it is restricted in this manner. If it is, see if the restriction can be modified to recognize the public IP that you use in your SNAT. If not, I'm not sure what can be done. :^(

j