A long time ago when I had a .Mac account, I decided to create an alias for a community web site. I do not remember when but all of a sudden I viewed pop up small windows showing that there was a problem with one of my aliases. I resolved this issue by deleting a number of SMTP servers. But I also wanted to manage the aliases that I had set up.
Alias Modify Procedure
Open Mail and select that application so the computer screen shows that menu at the top of the screen.
Next to the apple icon in the upper left corner of your computer screen is the menu option Mail and when your mouse clicks on that word “Mail” which will reveal a pull down menu selection. Please choose iCloud from the Accounts along the left side. You have three selection tabs on the center right. Choose Account Information. This part of the screen is chopped up with thin lines into four sections. Look at the top section with the label Account Type: IClouid IMAP. Now three lines down you should see “Edit Email Aliases…”
Mouse click on this button. This will activate a web browser and send you to your iCloud login page. Login to your iCloud account by entering Apple ID and your password. Your apple ID is your mac mail address “<name>@me.com”. Select Accounts button.