Flooded With Mailer-Daemon Failure Notice Spam

By Adrian Grahams

Updated September 28, 2017

Mailer-Daemon programs reject spam emails and notify the sender.
i Medioimages/Photodisc/Photodisc/Getty Images

Receiving multiple mail messages from a Mailer-Daemon in your email inbox means that email messages from your email address have been rejected and bounced by the recipients’ mail servers. If you receive many Mailer-Daemon messages, spammers may have used your email address to send out large volumes of junk mail.

About Mailer-Daemon Software

Mail servers use Mailer-Daemon programs to receive incoming mail and distribute it to the correct recipients. If the address is incorrect or appears on a blacklist of known or suspected spam addresses, the Mailer-Daemon rejects the message and sends an email notification to the sender with “Mailer-Daemon” in the message’s Subject and From fields. Occasional Mailer-Daemon notifications might indicate that you’ve incorrectly addressed an email, while a deluge of notifications suggests that your email address or domain has been used to send out spam.

Email Blacklists

Many large organizations and email service providers try to reduce the problem of spam emails by subscribing to email blacklists that contain the email domains or specific addresses of known spammers. Your email address can end up on a blacklist through no fault of your own. Sharing an email domain -- the part of the address after the “@” symbol -- with a known spammer can lead to blacklisting. You can use an online blacklist check service to find out if your email address or domain has been blacklisted and then ask your email service provider to have your address or domain removed from the list.

Spoofed Email Addresses

Spammers sometimes try to get around blacklists by spoofing a legitimate email address to make it appear that the spam email comes from a different address. One spamming technique is to use automated programs that send out hundreds of thousands of emails to randomly generated email addresses. Because many of the email addresses aren’t valid, the Mailer-Daemon rejects the email and notifies the sender. If your email address has been spoofed in the “From” line of the spam email address, you will receive multiple Mailer-Daemon notifications.

Computer Viruses and Email Spam

The worst-case scenario is that the mail program on your computer has been infected by a virus or other malicious software and is sending out spam emails without your knowledge. The Mailer-Daemon notifications occur when the program recognizes the emails as spam or because the compromised mail program is sending to nonexistent addresses. If you suspect that a virus or malicious software is to blame, install anti-virus software or update your existing program and then carry out a full scan of your computer system. The anti-virus program will detect and delete infections. Use free anti-virus programs, such as Microsoft Security Essentials, AVG or Avast, or invest in a premium anti-virus program to secure your system. In addition, activate your Windows Firewall.