Form gives users error email

Hi, ive set up a simple form, but whenever anyone completes it they get the following email:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. The following address(es) failed:

info@mylocalfloristnetwork.co.uk No Such User Here

Is this more of a server/host thing or is there a conflict with Perch somehow?

Thanks