Ronald sends in a desperate query - "By mistake I deleted a bunch of emails when working last night. Is it possible to retrieve a deleted Yahoo email message?". Unfortunately there is no direct and simple answer to his question is... it depends whether further housecleaning has been performed - has the Trash been taken out?
All email accounts from Yahoo! come with 5 default folders - The Inbox, Drafts, Sent, Span and Trash. Deleted messages are moved to the Trash folder so if you want to retrieve an email all you need to do is to go to this folder, drag-n-drop the message back to the inbox. Voila! Your deleted email message is recovered. (Drag-n-drop only works on the All-new Mail Yahoo interface version.)
An alternate way to shift a message from Trash to the Inbox is to Move it which works on both the Yahoo Mail versions.

However, as I mentioned above, if the trash folder has been emptied, there is no way an email can be retrieved and the only option is to ask the sender to forward it to you once again.
Accidental deletion of email is a not-so-uncommon problem. Unfortunately there is no way to recover an email that's been trashed unless it first goes to an intermittent "Deleted Items" / "Trash" folder before you are able to get rid of it completely.
Here is a little tip: Maintain two or more copies of all important email correspondences. If you are a prolific user of the Yahoo service, I suggest you upgrade to Yahoo! Plus which will let you download Yahoo email and store them on your computer with any email program such as Outlook Express, Outlook, Thunderbird. Plus upgrade costs a little less than $20 annually and is worth the money because of sheer convenience. However, if you don't want to spend a penny, I suggest you download and install the free Yahoo email program - Zimbra desktop with which you can access the account for free.
Page contents: Retrieve deleted Yahoo email: recover a message that has been accidently removed from the inbox.
Comments, questions, feedback... whatever!