trevorwood on "[Plugin: Contact Form 7] Contact form 7 won't send to email address on office 365"

I've got a form that works fine when sending to a normal POP3 email address. However, when I send it to an email address that's inside office 365 I get the message "Failed to send your message. Please try later or contact the administrator by another method." in a red box.

Any idea why it might be failing?

http://wordpress.org/extend/plugins/contact-form-7/