Mail that you do not delete immediately can come back to haunt you later on. Likewise losing a message by accident when you intended to keep it can be a big problem. The Trash folder in Yahoo! Mail helps you prevent such inconveniences. In many cases, you will be able to either recover messages or manually delete them yourself.
All deleted mail in Yahoo! Mail initially goes into the Trash folder. The Trash is a system folder like the Spam and Inbox folders. Yahoo! informs its users that this folder is emptied automatically from time to time. There is no way to set or extend the time a message may remain in this folder. If you leave your deleted messages there, they will be removed sooner or later. This action permanently erases those messages from Yahoo!'s servers and cannot be undone.
Deleted messages are still under your control for as long as they appear in the Trash. If you want to erase them immediately without waiting for Yahoo! to make its occasional purge, click the "Empty" or dustbin icon next to the folder's name on the left navigation bar and click "OK" to confirm the action. But if you want to recover a message, select the message, click "Move" and choose the folder to move it to (such as the Inbox).
The Spam folder works differently from the Trash. Yahoo! filters suspected junk mail as well as mail you have manually labelled as "spam" to this folder. Yahoo! keeps items in the Spam folder for a month by default. To change this setting, go to "Options" > "Mail Options" > "Spam." Next to "Empty spam folder," select the desired period from the list. Like the Trash, contents in this folder can be manually deleted.
Because Yahoo! periodically clears the Trash without warning, you should not expect mail to remain there for any length of time. Instead verify that you are deleting only what should be deleted. If you remove a message by mistake, recover it as soon as you can. With regards to the Spam folder, be careful about deleting mail from there. Sometimes Yahoo! misidentifies legitimate mail as junk and sends them to that folder. Inspect your Spam folder every now and then or when you are expecting a message that does not arrive.