In the future, you can set up your email client to use IMAP and delete the mail from your computer. That probably wouldn't have worked here since it was already so far gone, but consider using either IMAP on your computer, or GMail, Outlook.com, etc. POP3 to pull the emails from your account. GMail and etc. will delete the mail as it comes in, spam filter it, and deliver it to your inbox like regular mail. You can also send mail *outwards* from these services, so it looks like you sent it from [your domain].x10.mx instead of gmail.com, outlook.com, etc.