Why would you consider sending an email to an address that you know does not exist within the company you are performing a Penetration Test for?

Bounce messages reveal MTA and routing information, not the identity of the root account holder.

Sending a single email to an invalid address does not generate enough load to constitute a denial-of-service attack.

The goal is targeted intelligence gathering about the mail server, not generating unsolicited bulk mail.

When an SMTP server receives mail for a non-existent recipient, it returns a bounce or NDR message. This error response often contains the mail transfer agent (MTA) name, version number, internal hostnames, and relay paths - intelligence that helps a penetration tester map the email infrastructure and identify exploitable software versions.

Virus protection testing requires sending a known-malicious or EICAR test file as an attachment, not an undeliverable address.