Hi victor2868,
As we understand it, you want to know if you can use a different port for SMTP for your iCloud Mail account, correct? We have some resources we'd like to share that could provide some good information.
This link mentions that port 587 is required for "iCloud Mail (SMTP authentication." TCP and UDP ports used by Apple software products - Apple Support
This might be useful:
Some software might use different ports and services, so it can be helpful to use port-watching software when deciding how to set up firewalls or similar access-control schemes.
Some services might use more than one of these ports. For example, a VPN service can use up to four different ports. When you find a product in this list, search (Command-F) in your browser for that name, then repeat your search (Command-G) to locate all occurrences of that product.
Some firewalls allow selective configuration of UDP or TCP ports with the same number, so it's important to know the type of port you're configuring. If your firewall doesn't allow you to specify the type of port, configuring one type of port probably configures the other.
This guide providers further information on iCloud Mail server settings for other email client apps - Apple Support
If this doesn't answer your question, please contact us directly with this link: Apple Support
Cheers.
