Eric Shields | Mass Transit Honchkrow:
> Hi again. I finally figured out that my firewall rules might be the
> reason my connection times out. So when I send an email, it doesn't get
> past the SYN_SENT stage of the TCP handshake. In addition, it does not
> leave my NAT device.
ISPs for residential networks often block outbound traffic to TCP
port 25, which leaves the sending system in the SYN_SENT stage.
You can test that with netcat (command: nc mail.example.com 25).
The 'fix' is to send mail through a provider's mail submission
service on TCP port 587 or 465.
Wietse
