I run an OpenBSD/courier-imap mailserver at home with a pf firewall. When I run a Thunderbird client on my Linux desktop at home things are fine. Both machines are behind a Linksys firewall.

When I run Thunderbird on my desktop at work and try to reach my home server, it runs fine for a minute or two and then loses the connection (connection to server timed out). All this is secure (SSL) imap through port 993.

Any idea what the problem might be? I don't see any rules in my pf.conf that would cause a broken connection, and FWIW, I can ssh from my work desktop to my home server and stay logged in without losing the connection. I also don't see anything in /etc/courier-imap/imapd* that would cause remote connections to timeout but not local connections.

Thanks.

For the benefit of any others with this problem...

The issue is the Linksys router/firewall. There's some bug in the firmware which causes trouble with secure imap when stateful packet inspection (SPI) is turned on. The firmware is closed-source and so cannot be debugged. However, turning off SPI solves the problem. Note that the "disable firewall protection" checkbox (Security->Firewall) only turns off SPI, it doesn't actually disable the firewall.

GR