Undeliverable Notifications may be due to Email Spoofing
IMSS has received reports of people receiving bounce-back undeliverable notifications that suggest they sent an email containing malware. Some people have been alarmed because they know they did not send the original malicious message. Most likely, the email address was spoofed, which means a spammer forged the “from" email address to mislead the recipient about the origin of the message. Spammers and email-borne malware often set the sender address to match the recipient's address, in hopes that the recipient will be confused and open the message.
Unfortunately, even if you did not send a message containing malware, you may still receive an undeliverable notification if your address was spoofed. If that is the case, which you can verify by checking email headers, you can simply delete the notification message. If you have any questions or need assistance, please contact us (x3500, firstname.lastname@example.org, https://help.caltech.edu).