Thanks for the response.
Unfortunately, it did not resolve my issue.
I am using the full featured version of yahoo and I have switched between the basic mail and newest Yahoo Mail to be sure.
The option 'Email Alias' is simply not listed under Mailboxes.
I have two yahoo email accounts. I can see 'Email Alias' in one account but not the other account where i need it so this is definitely missing / not listed for selection.
I would appreciate any other solution pls