Re: deleating multible emails on my Droid Turbo
For some reason, Yahoo doesn't expose their own spam folder to IMAP, so, no, you can't with any non-Yahoo mail client. You can, however, create your own folder called, say, "junk mail" and move messages there. It doesn't "train" the spam filter, but then you can always mark the messages as spam the next time you use a pc browser to connect to yahoo mail.
(I have a rule in my yahoo account to forward all yahoo messages to my gmail account. In my gmail account, I have a filter to put those messages in their own label when they arrive, plus I have gmail set both to reply from the account that messages were sent to and to allow gmail to send from my yahoo account - these are all things you set from gmail settings on a pc browser. This gives me only one email app on my phone, PLUS the added benefit of Gmail's fantastic spam filters, which nobody else beats.)