remove messages from server imap smtp

I dont have POP3 activated on 1and1.com. Im using IMAP/SMTP as set up by the email client.  I want to have it delete the emails off of 1and1 once Ive downloaded them.   I cannot seem to find a setting in IMAP/SMTP to do that.  What am I missing. 

Anyone?

You have to setup the account as POP3, otherwise, IMAP will just do a sync. You cannot activate or change the existing account to POP3, you will have to recreate it. Don’t use automatic setup. When you add the new account, click on mail and select other. Make sure the option to save messages on the server is deselected.