Cannot send mail from macbook when connected to internet via iphone 5 hotspot

Cannot send mail from macbook when connected to internet via iphone 5 hotspot

Emails will send fine direct from my phone 5, but remain in outbox when I try to send from my mac book.
I get an authentication error, but I have double checked all settings and they are all correct, as far as I know.

Is it not possible to send emails from a tethered phone? I would have thought it would be fine as emails are received ok?