SMTP Auth Failure "containing virus.

Guys, regarding FORTIMAIL, I tell you that today, the alert has been received that a provider the client works with has received an email from a user of your company's domain, with the subject: " SMTP Auth Failure "containing virus. Reviewing the AntiSpam it is found that the user has been sending this type of emails, however the antispam has been blocking it. There are other users of the client's company domain who are trying to send the same email and the antispam is rejecting it. DO YOU KNOW WHAT THAT MAIL MEANS? "SMTP Auth Failure" containing the virus? SOMEONE HAPPENED THE SAME?