What I wanted to do is to insert my customer name in the plain text Email that Zabbix sends to our ticket system. (This way it can auto sort it to the correct customer).

So what I did was "clone" the Alerts/Media Type/Email media type and created a new Email media type, calling it <Customer Name> Email. I then modified the email template of the new media type to inset our customer name for both the "Problem" and "recovery".

See Below:

Problem - Logical - : {EVENT.NAME}

The customer in this instance being "Logical"

Under the trigger action I then selected the user to send email to and the media type to use (being the custom one made above).

When it sends the email I get the error "No media defined for user."

If I modify the trigger action back to the default "Email" media type (and don't change the users it is sending to) it sends the alerts fine.