I’ve said before we had gotten reports from people that voluntarily participate in the Kolab Now Beta Programme, that the iPhone iOS and Mac OS X Mail.app were not really happy using IMAP over implicit SSL (you know, the one on port 993). Here’s a summary of the things that have happened thus far;
Supply Erlang 18.3, for its more reliable and modern SSL implementation. Ensure the TLS ciphers available / configured are above board. Ensure the server isn’t waiting for any client certificate. Honor the server-side priority of ciphers. Do not allow renegotiation. Disable compression. Examine telemetry on the actual Cyrus IMAP frontends used. And so on and so forth. And then some.
For now, it seems it is just a tiny little digression in tagging IMAP commands though. We’ll obviously keep you up to date, should we discover more about it and perhaps even resolve the problem.