We have had a number of queries from Spark (formerly Telecom New Zealand) customers, regarding sending emails via Sparks SMTP server.
Recently Spark reconfigured their SMTP service to require encryption. Prior to MoneyWorks v7.1.8, the included SMTP mail client on Windows did not support encryption, so the first step if you are on Windows would be to install sendEmail.exe, which does (see this FAQ. Or, simply update to MoneyWorks v 7.1.8.
Then, set the server name in the MoneyWorks emailing preferences to send.xtra.co.nz:587. The server on port 587 is compatible with the STARTTLS protocol that sendEmail uses.