Change Target port SMTP MTA to internal Exchange

Hi Sven,

Thank you for reaching out to Sophos Community.

Have you tried to use any how-to videos, documentation, Sophos Assistant, or KBA to try to check the issue?

Can you share your configuration and FW rules?

Then kindly try to turn off the smtp on the Device access, then check and test.

You may also refer to the following KB 

support.sophos.com/.../KB-000038880

Hello,

How to Nat is known well.

I like to Nat the smtp MTA proxy sending port 25, when send mails to exchange, from target port 25 to port 5252.

I have setup a NAT rule, Firewall IPs as source, destination Excachenge, dest port 25, to port 5252, and I have a firewall rule allowing this traffic.

But it is nor working.

Sven

Hello Sven OlafSchuran ,

Sophos Firewall inspects all SMTP/S raffic on the standard ports by default. Now you can use service-param to turn on inspection of traffic
sent over non-standard ports. Now if the port used 5252 is not working for the SMTP/S it would be great if you can try telnet or capture traffic on that port to understand the traffic flow - https://support.sophos.com/support/s/article/KB-000035768?language=en_US

Create and download a packet capture : https://support.sophos.com/support/s/article/KB-000037007?language=en_US

I have MTA mode running. When MTA mode sending Mails to internal Mailbox Excahnge it uses port 25. This is working as it should.

But to get reicipoient filter working I must send send Mail to the internal exchangfe server via port 5252. I have done this in SG UTM witrh a NAT rule, I am trying it the same way in XGS. But NAT is not working.

Sven

I have MTA mode running. When MTA mode sending Mails to internal Mailbox Excahnge it uses port 25. This is working as it should.

But to get reicipoient filter working I must send send Mail to the internal exchangfe server via port 5252. I have done this in SG UTM witrh a NAT rule, I am trying it the same way in XGS. But NAT is not working.

Sven

Hey Sven OlafSchuran  try the steps mentioned in the following steps: https://doc.sophos.com/nsg/sophos-firewall/19.5/help/en-us/webhelp/onlinehelp/AdministratorHelp/RulesAndPolicies/NATRules/RulesPoliciesCreateDNATAndFirewallRulesForInternalServers/index.html

I do not want external to internal.

I want internal firewall IP destination port 25  sending to internal exchange changed to port 5252.

I have a NAT Rule but it is not working.

Please show a screenshot of your NAT rule. 

Hey Sven OlafSchuran , mention the smtp_5252 in the original service and the under the translated service (PAT) SMTP_25

I smtp MTA on XGS shall send its mails to exchang server on port 5252. Standard port is 25. So I must change 25 original service to port 5252. Your Idea is changeing 5252 to 25.

Yes Sven OlafSchuran 

Try to change the source to ANY and only destination your exchange server. Check in the logs, if this changes the port or not. you can also verify via conntrack, if the NAT is applied or not.