Can't connect to port 143 on external host

Hi all,

 

I have a Sophos XG with SFOS 17.5.8 MR-8, and everything is by default.

I have one nat rule to all hosts/ports to go out to the wan.

My issue is that I have a internal host, an IOT device, that needs to communicate with port 143 on the wan and its not able to, I see the package being accepted on the logs but no reply from target. Checked With tcpdump on other host trying telnet to the same target and no replies are getting in.

Tested without Sophos and it works. I can't see any traffic being denied anywhere.

How can I find in which layer it's being rejected?

Thanks