Email+ uses the vendor, Sparkpost, for the delivery of emails. Each 'from address' domain needs to be approved and setup by Tech Services before an email can be sent from that domain. The following domains will not be approved for 'from addresses' in Email+:
mx.uillinois.edu
ad.uillinois.edu
Request an alias
However, you can request, with the below Tech Services form, an @illinois.edu alias email address that can be used in the 'from address':
https://idm.cites.illinois.edu/requests/group-alias/group-alias-multi-web-request-form.cgi