2d, iPhone and wifi email set up help.

After some help to set up email on my iPhone.

In coming is joeblow@companyname.co.nz, mail.companyname.co.nz etc

Outgoing pop is set to smtp.2degreesmobile.net.nz

Which is all good.

However when I am at home and hooked up to telstraclear wifi it won't let me send emails unless I turn off wifi and send 3G. How can I change this ? Or is. It an issue with TC ?

Cheers