Hi,
I am Subscribed to any Thread I have posted in so any new post I get an email notification.
(In the case of the iChat Community, I am Subscribed to the whole community (termed Following) so I get notifications of all new post there).
You do get 90 Days Apple Care when you buy a new product, be it Hardware or Software.
Apple ID issues are free to fix any time.
You can call Apple Care at other times and arrange to pay for the assistance.
Mail in Sierra
You need to go to the Mail App in the Menu Bar and select Preferences that Accounts.

Choose the last tab (Server settings) in the pic above and then use the drop down and the Edit option
Alternatively some account will show the details they are using.
This account uses a different server for outgoing mail. (I originally did not pay for that service on my Web site)

You can select the Outgoing Account here and get to the same Edit option.
You need to enter the STMP server name
You need to enter the Port being used.
You need to mark if it is using SSL or TLS as a secure login.
In Yosemite some of these setting are in the Advanced tab.
In either case you will need to know the STMP server name of the service you use.
You will need to know the port.
You will need to know if they use SSL (Most do).

8:38 pm Monday; September 26, 2016
iMac 2.5Ghz i5 2011 (El Capitan)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
iPhone and an iPad (2)