We are currently looking in to an issue with our SSL certificates for IMAP and POP. Although for most people this doesn’t affect these services in a noticeable way, some email clients may report an error. We are working to resolve this issue and apologize for the inconvenience.
Update 11:52 CEST – This issue has been resolved now. You can find certificate details on this page: https://help.runbox.com/runbox-server-certificates/