A working incoming connection is a chain: the client listens, the computer allows the traffic, and the network sends it to the right device. A forwarding rule addresses only one part of that chain.
Use your own port settings
Read the TCP and UDP values under eMule's connection preferences. Old examples often mention TCP 4662 and UDP 4672, but the values selected in your installation are what matter. Write them down before changing the firewall or router.
TCP and UDP are different protocols. A rule for one does not automatically cover the other. You do not need to expose every port mentioned in an old tutorial, and the web-interface management port is a separate feature from ordinary file-sharing connectivity.
Understand an example forwarding rule
Suppose your client uses TCP port 4662. A typical manual rule forwards incoming TCP traffic on external port 4662 to TCP port 4662 on the computer running eMule. The destination must be that computer's current local network address.
If the application uses a different value, substitute it throughout the example. A separate UDP rule should match the UDP value you recorded. Router interfaces use different labels, so review the meaning of each field before saving.
Keep the device address consistent
A forwarding rule can stop working after a router assigns your computer a new address. A reservation in the router's DHCP settings can keep the chosen device at a consistent local address. Do not change unrelated network settings just to follow a screenshot from another router model.
When testing, use the connection you plan to keep using. Switching between Wi-Fi, Ethernet and a VPN may change the path and make an earlier result irrelevant.
Check the application rule on the computer
Windows Firewall needs to allow the correct executable on the intended network profile. If you installed eMule in a new folder or changed builds, inspect the rule rather than assuming an old entry still applies.
Third-party security software may have its own application control. Check its relevant rule if present, while keeping the wider protections enabled. Creating many duplicate rules makes the final configuration harder to understand.
UPnP, double NAT and provider NAT
UPnP can ask a compatible router to create mappings automatically. If it does not produce the expected mapping, inspect the router result before also adding a manual rule. With two routers, both layers may need attention. With provider-side carrier-grade NAT, a local rule may never be enough.
These are different causes with different remedies. The Low ID checklist helps separate them.
Test with the client running
A test checks whether a particular service can reach a port at that moment. A closed application, changed network route or temporary connection problem can change the result. Run the appropriate test with eMule listening, then confirm the connection status inside the client.
After a successful result, keep a note of the working values. If the problem returns, compare the current configuration with that note before making more changes.