Tesserax,
I have six AOL accounts. In several if not all of these accounts I received the same message that BarryMacMan did. I'm running Sierra 10.12.6 with Mail v10.3 (3273) on a Retina 5K, 27-inch, Late 2014 iMac. These AOL mail accounts have worked fine for many, many years on my Macs and iPhones/iPads. I use the AOL accounts ONLY for email.
I do not have all of my AOL accounts installed on all of my Apple devices. To test your instructions, I added an AOL account not previously residing on my iMac. Following your bullet 3, BEFORE clicking on Sign In, I held down the Option key and then clicked Sign In. I did not get the opportunity you mentioned to edit any settings. Instead, I got this:
I deleted the newly-added account and tried a second time with the same result.
When I go to Mail > Preferences > Accounts, select any AOL account from the left hand column, then Server Settings and scroll down to the bottom of Outgoing Mail Account to get to Edit SMTP Server list, NONE of my AOL accounts appear in the resulting window. The only accounts shown are my local FreeNet's POP accounts and my iCloud account (but not my @mac account).
I don't find any way to view or edit the settings on my AOL accounts.
Any help or suggestions will be greatly appreciated as not only do I have to manage my AOL accounts, but I am the "Sys Admin" for my wife, my daughter and my granddaughter, all of whom have Macs and iPhones with AOL accounts.
Thanks a lot!
Don