You don't most likely need any Lotus developer, just a workflow guy, who knows few tricks (mentioned already in the earlier answers). Eventually you just need to a send an email to an external email address (and the email client being Lotus doesn't have pretty much any role in this).
Most probably the extended notifications (SWN_SELSEN) is the way to go. You can set it up to send emails of users work items.
Regards,
Karri