How can we allow users to send email requests without requiring them to create an account?

[Info Tech]

We have added trusted domains and would like to have our users be able to send email support requests from those domains, without needing to create an account. How can we set this up?

If this is not possible then we need to be able to create their accounts without their interaction, so they are able to send emails to our helpdesk. Any help would be appreciated. Thanks.