Since port 25 is blocked on my VPS, I need to configure Postfix to send emails to other ports such as 587 or 465. But it seems most incoming SMTP servers on the Internet such as outlook or gmail do not open port 587 or 465. They just use port 25 to receive emails. Is this a common practice?
I do not mean to use another SMTP server to relay emails (as talked in this post.)
Another question is if all(or most) SMTP servers that open port 587 need authentication? Port 587 is called submission port so I think it asks you for account information. Is there any incoming SMTP server that uses port 587 to receive emails and does not need account authentication?