[Exim] Setup secure SMTP for XP/Outlook

I have a couple of clients who need to be able to send mail through my
server. Up to now I have been using cram-md5 authentication, but this
does not look like it is available for XP/Outlook.

Is the best combination plain text authentication over SSL?

Thanks for any comments.
Rory
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Rory Campbell-Lange
<rory@???>
<www.campbell-lange.net>