Citadel Imap and Mac OS/X 10.6.5 Mail.app

I don't use Mac but hopefully these steps will help you with debugging if the issue is in your firewall.

Try installing Thunderbird for a test. If that can't connect then either Citadel is not configured right or your firewall is not opened up for port 993 traffic.

To check if iptables is allowing traffic run:

sudo iptables -L -n | grep 993

You should see:

ACCEPT tcp – 0.0.0.0/0 0.0.0.0/0 tcp dpt:993

ACCEPT udp -- 0.0.0.0/0 0.0.0.0/0 udp dpt:993

Good luck.

Thanks for the idea, but in my case I have Mail.app configured to talk on port 993 for other mail servers on other sites, so I know 993, and 465, and 567 (?) are not being blocked. But setting up Thunderbird might give me a clue.