SMTP System Settings

Really struggling to get SMTP System Settings right in order to use FormIt. Could someone please shed light on things, this is what I’ve input (obviously not exact name of site or password!) - don’t think this is correct as I still can’t get Formit to send!

mail_use_smtp - yes
mail_smtp_auth - yes
mail_smtp_host - smtp.example.co.uk:25
mail_smtp_username - bob.example.co.uk
mail_smtp_password - password
mail_smtp_port - 25
main_smtp_prefix -

Thanks in advance