Hello,
Well, I had a long support request put in, but I ended up solving the problem myself. So for any future eM client users: if you are having trouble connecting to IMAP on your Pobox Mailstore account, check that the following are true:
- The port is set to 993
- Security policy is set to “Use SSL/TLS on special port (legacy)”
In particular the second point is important.
Good luck!