Mail will not send

I have just bought an amazing Imac and have managed to set the incoming mail but when i want to send a message it says the SMTP is offline, not sure what to try now, any ideas?

Have you been into Mail Preferences to put in the SMTP settings for your ISP Mail account;


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In Leopard I had my SMTP set to Authentication "None." When I upgraded to Snow Leopard I had to change that to Authentication "Password," and put in my ISP email account username and password. Check your settings. To find them you have to drill down under the edit SMTP server list.