Hi Really Needy,
Thanks for coming to Apple Support Communities for help with iCloud Mail. It sounds like email isn't sending after the recent update.
You shouldn't need to edit any server information for iCloud. Try going into System Preferences > iCloud and unchecking Mail. Reboot the computer and check Mail again in System Preferences > iCloud and see if iCloud Mail starts working again in the Mail app.
If you still have the issue, sign completely out of iCloud: Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV, or Mac. Then sign back in and test once more.
If the issue continues after that, try isolating the issue a little further and test inside a new user account. You can sign into iCloud in that user and see if iCloud Mail functions as it should. This will let you know if the issue is system-wide or isolated to the user account. Here's how: How to test an issue in another user account on your Mac.
If your father-in-law needs to access any mail before you can help him with this, he can always get it on iCloud.com through his web browser.
Let me know how it goes.
Have a fantastic weekend!