The SMTP host is your 'Outgoing Mail Server' for your Internet Service Provider. If you already have a working e-mail account then you can get this info from your e-mail program. If you have Outlook Express, click on 'Tools', 'Accounts', click on the 'Mail' tab in the upper left of the window, click on your e-mail acount, click on 'Properties', then click on the 'Servers' tab in the upper left area, and look in the box that's labeled 'Outgoing mail(SMTP)'. Inside this box should be the name of the SMTP server.
If this doesn't help, you should contact your ISP and ask them what thier SMTP server name is.
If you are hosting your e-mail in-house then you need to talk to your mail admins for the info.
Good Luck!