I'm trying to check that my imailds mail software, which sits on my
BM37 server is not relaying mails.

If I run one of the online mail relay testers or trying a manual
telnet test, I get a "could not open a connection to host on port 25.
Connect failed" error.

I'm assuming this is because the default smtp port filter is blocking
the communication and therfore preventing the server acting as a mail

The filter is:

source interface: public
destination interface: all
pkt type: smtp-st
src addr: host with addr of public interface
dest addr:any

Am I right?