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If anyone can assist - I am running an internal network that is primarily used for POP3 Messages and a couple of other TCP/UDP services. Until recently the whole network (shared by two different departments) operated on a range which worked fine for what was needed of it. Then recently it was wanted that a firewall with ACL was insterted between the two departments and one NW became (LAN side) and the WAN side became The firewall bought and installed is a simple Lynksys RVS 4000 Router with firewall and ACL capabilities. Both the LAN and the WAN have their own SMTP servers that run a program called JSMAIL (as previously). The ACLs were written to allow POP3 and SMTP in both directions between the servers. The c:/windows/system32/drivers/etc hosts file was amended for both SMTP servers to point to the correct IP range. Permanent routes were added to both SMTP servers to be able to find the correct port of the Lynksys WAN or LAN as appropriate.

But right now the WAN side users can send messages over the LAN side, WAN to WAN is ok, LAN to LAN is okay but LAN to WAN bounces all messages back! I am most perplexed by this and cannot figure out what I am doing that is wrong. I have checked and rechecked all of the settings mentioned above but I must be doing somethign stupid that I cannot get the messages to go from LAN to WAN but I can do the reverse..... Please help.

- Both SMTPs are Windows XP Machines. the rest of the workstations on WAN and LAN are a mix of XP, 2000 and even one or two NTs - but the other clients should not be pertinent.

The Network is not on any kind of domain nor are there actual Servers - just a number of stand alones.
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Thanks VM. It was an ACL on the firewall. a third server was setup that I did not know about and the IP routing tables showed that it was blocking syn messages to that one. When this was resolved all started woking well.

A router is a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. The most familiar type of routers are home and small office cable or DSL routers that simply pass data, such as web pages, email, IM, and videos between computers and the Internet. More sophisticated routers, such as enterprise routers, connect large business or ISP networks up to the powerful core routers that forward data at high speed along the optical fiber lines of the Internet backbone. Though routers are typically dedicated hardware devices, use of software-based routers has grown increasingly common.

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