Hi Gill,
You can't send a text message to an email address as such, the only way you can do it is by sending a MMS instead.
Just start a new multimedia message, type all the text you want, you're not restricted to the 160 characters, with a MMS it's a limitation to the size of the message in kb. Where you would type the mobile number in you add the email recipiant instead and the MMS will be sent to the email address you've specified. You shouldn't need to specify any email centre in the MMS, what your phone seems to be asking for is the email client details for setting up your own email account on the handset. The person recieving will get en email from "
[email protected]" or similar, they won't be able to reply to the email though, currently it's only one way, mobile -> PC. If you're wanting to set up email proper on the handset it's as simple as copying the settings from outlook into the handset, then you can pick your email up on the move!
Hope that helps.
G