Some customers cannot change the sending name for business email aliases in the Webmail interface, Settings menu, on the Accounts page.
We are investigating this problem and working toward a resolution as quickly as possible.
(08/12/15) Our mail engineering team is continuing the investigation for this matter. We will post further updates as they are available. Thank you for your patience.05:56 PM PST
(08/18/15) We understand how frustrating this issue has been and appreciate your patience. We have identified the issue blocking users from viewing the correct Sender Name for aliases in Business Mail accounts. Yahoo Mail is working on a fix for this issue and alias names will be restored by the end of the week.03:42 PM PST
(08/27/15) We have removed the automatically generated Sender Names from all aliases that were impacted. We are now in the final stages of restoring the original custom Sender Names to the Yahoo Business Mail aliases.
We will update you with more information as it becomes available. We apologize for the inconvenience and thank you for your patience.