Show source IP behind NAT

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maruscya
maruscya Posts: 1
Friend Collector
edited April 2021 in Security
Dear Friends, 

I'm a newbie user of ZyXel USG-200. 

I need to reach SMTPs service behind the firewal. Following some guide i setup correctly the NAT service. 
Now the SMTPs is are available. 



I check the log on SMTPs server and all incoming connections comes from the IP of the firewall 

postfix/smtpd[8745]: DDEF012004D: client=unknown[192.168.1.200
postfix/cleanup[8746]: DDEF012004D: message-id=<CANRN+XAFW50ABRnW7Gcs7fB=0f1gOK7H_smb8a3VTTBqmGQQOQ@mail.gmail.com>
postfix/qmgr[381]: DDEF012004D: from=<*************@gmail.com>, size=3762, nrcpt=1 (queue active)

In this example the IP of google is replaced by the IP of the LAN of firewall (192.162.1.200).
I try to find how to resolve this issue by myself but without success. 

WAN2_IP : The public IP of firewall
LAN IP :  192.168.1.200 of firewall 
MailCow: IP of mailserver 

Can someone help me? 

Many thanks

AndreA

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