How to change smtp port 25 to port 587

My ISP is blocked port 25 to send mail and I want to change default port 25 to port 587, How to change?
Thank you
Best regards

Please describe the scenario.
Do you want to send or receive email?
In UCS, when the mail server app is installed, port 587 is open by default.

I guess that the question is related to the relayhost setting.
Postfix Small/Home Office Hints and Tips says:

I havent verified it, but it looks like adjusting UCRV “mail/relayhost” is the way to go.


Thank all I just tell ISP to unblock port 25 and then it work can send email with port 25