PepLink 310 - Outgoing firewall

I working on our 310 firewall to grant to a specific client [] access only to our SMTP server,
leaving other clients the option to reach all SMTP servers.

In the Outbound Firewall Rules i setup the four rules below:

CLIENT_SMTP_OK Source=[TCP: - Port:Any] / Destination=[TCP:88.35.xx.yy - Port:25] -> ALLOW
CLIENT_SMTP_NO Source=[TCP: - Port:Any] / Destination=[TCP:Any - Port:25] -> DENY
OTHER_SMTP_OK Source=[TCP:Any - Port:Any] / Destination [TCP:Any - Port:25] -> ALLOW
DEFAULT Source=[TCP:Any - Port:Any] / Destination [TCP:Any - Port:Any] -> DENY

The result is:

  1. the client does not reach NOTING on port 25 (not 88.35.xx.yy, nor other)
  2. all other clients reach ALL on port 25

What’s wrong ? :frowning:


Thanks Alex, any screen capture you can share of these firewall rules? And I believe your Balance 310 is running on our latest firmware 5.4?


Our PepLink 310 is a 5.3.9 firmware equipped:

… below a screenshot of the outgoing firewall with rules involved

… an then the result of client when telnetting our SMTP server (88.35.xx.yy)

Other clients reach our SMTP server and all external other too …


Hi Alex,

Your firewall rules look correct assuming your SMTP server is out on the internet and not inside your LAN. Please upgrade your Balance to the latest firmware and open up a support ticket with us at if there is still a problem with this.

Best regards,

The Peplink Team


Thank you for feedback.

The SMTP server address is one of the PepLink’s public address NATted on an internal ( IP of our LAN where our mail server resides.

Perhaps this could be the problem ? May i try to replace the public SMTP address with the internal IP ?


As far as I can see your SMTP server is on Peplink LAN. In this case then yes we should use its LAN IP for firewall.

In the firewall rule I replaced the SMTP public address with the private IP and finally all run fine !

Thank you for support ! :slight_smile:


No worries Alex. Just a misconfig. Enjoy your Peplink.