I tried adding the line trust.server.for.starttls=true in the server.properties file, but still get the error message "Unable to connect to server. java.security.cert.CertificateException: Certificates does not conform to algorithm constraints" when attempting import using SSL ON and port 993. That port is configured on the source server as "Init SSL/TLS ON". I'm puzzled why I can't just import using plaintext mode over port 143, which the source server is also configure to listen on, with "Init SSL/TLS OFF". But when I try that I get the error message "Unable to connect to server. STARTTLS failure".