Sending email using SeaMonkey

Strange. I just installed SeaMonkey v.2.0 and I use all email settings identically as for Thunderbird. In an office (work) environment TB allows me to write and send email "as though from home" (and still does, I just checked) but SM comes up with the following error message immediately after pressing :

Sending of message failed.
The message could not be sent because connecting to SMTP server smtp.blueyonder.co.uk failed. The server may be unavailable or is refusing SMTP connections. Please verify that your SMTP server settings are correct and try again, or contact the server administrator.

Settings identical to TB (I checked). I know from experience that the "server administrator" won't assist with problems relating to portable software and ansolutey certainly won't bughunt a phenomenon where one application (TB) works and an identically parametrised alternative (SM) does not.

Q1 Any ideas?
Q2 Please could SeaMonkey have its own forum page?

Thank you!