Fixing mail-sending problems on Wanadoo Broadband

For weeks now I've been having problems with sending email on any account and on any mail app while at home. I assumed it was something to do with Mail not being happy behind two firewalls and a router. Thus I was content to use webmail. Then it came to me, telnet the server and see if any errors are returned. For those lost already, 'telnet' is an app that lets you communicate directly with a server.
Anyway, I entered the following into the Mac's Terminal:

> telnet smtp.mac.com 25

(using smtp.mac.com as an example, you can try any SMTP server)

I got this:

Trying 17.250.248.48...
Connected to smtp.mac.com.
Escape character is '^]'.
554 Please check your SMTP server is set to smtp.wanadoo.co.uk. Further help is available at http://www.wanadoo.co.uk/......Long web address that messes up my lovely blog
Connection closed by foreign host.

Turns out you must use Wanadoo's SMTP server no matter what account you are using. Something I must have missed along the line.
Amazing what a little elbow grease will get you.

Anyway, the relevance to the world is this, if you have problems with sending email. Try this, if everything says 'OK' then I can't help, but once in a while a helpful error message lets you know what is wrong!


P.S. Apologies for the string of technical posts, but I just got my new iMac and am fiddling with a lot of settings. I'll have something more interesting to say eventually!