When you pop your e-mail using NZservers SMTP mail server you will need to Authenticate your e-mail before your send e-mail.

What happens if you don't do this?
If you don't do this and you attempt to send e-mail the e-mail will initially fail.
When you you then receive mail the mail A/C is then authenticated, allowing you to send mail the 2nd time round.

Steps to setup mail Authentication Outlook Express (Mac Instructions scroll down)

Choose:-

1. Tools
2. Accounts
3. Mail
4. Select Properties
5. Select Server tab
6. Select the check box - my server requires authentication
7. Select the settings tab
8. Make  sure the radio button is selected that says - use the same settings as my incoming mail server

Steps to setup mail Authentication Outlook Express - MAC

Outlook Express 4.0 and 5.0 (Mac)

Mac versions 5.0 and later of Outlook Express support SMTP AUTH (although versions 4.01 and earlier do not appear to do so)