A blackhole email address is as an e-mail address that when emails are sent to, they are immediately discarded.

This is particularly useful for sub-production instances where you want emails to be sent/processed, but do not want them to leave the ServiceNow mail servers.

Most of the time, this is configured on SMTP mail servers by specifying a certain email addresses or a domain.

ServiceNow has the following configured on the SMTP mail servers.

# blackhole domains 
example.com discard: 
.example.com discard: 
test.com discard: 
.test.com discard: 
nobody.com discard: 
.nobody.com discard: 
dummy.com discard: 
.dummy.com discard: 
yourcompany.com discard: 
.yourcompany.com discard:

Aslong as the email address ends with any of the above mentioned domains, it will be discarded by ServiceNow's SMTP mail server.

ie. nobody@example.com; john.smith@dev.example.com; blackhole@acme.yourcompany.com;