Ideally, you are using email under a domain name that you control, preferably hosted in an NSA-free zone with a company you trust (hint, hint). Most domain packages at easyDNS come with hosted IMAP included.
But if you must use a third-party email provider, you can setup your email forwarding here with a public GPG key, which our system will use to encrypt any email destined for you before the next hop.
This is obviously not an end-to-end encryption solution, however it will protect your data-at-rest on third-party email servers from prying eyes and data-mining.
GPG encrypted email forwarding is supported in the Standard DNS, DNS Pro and Enterprise DNS packages.