Mail Spool Issue

Hello Everyone 

i have exchange server 2016 behind sophos xg 

and the xg is acting as MTA 

exchange server SMTP port is 25 and iam using smart host relay to send mail over port 587 and everything was working like a charm 

till the ISP blocked port 587 and i have to change to port 465

so i changed the smart host relay in firewall to port 465 but the outgoing mails keep failing 

so disabled the smart host relay option form the Xg and changed the exchange server SMTP port to 465 

but here is the issue 

the mails doesnt reach to mail spool in the XG 

it only reach if i changed the exchange smtp port back to 25 

so my guess is the xg is listening to port 25 

is there anyway i can change it to 465 ?

thank you