From Clutter Free PC :
“Help! There’s a demon in my mailbox!”
Email users may have received a confusing message in their inbox from a mysterious address called MAILER-DAEMON. The message typically comes in response to an email previously sent by the user. The email that comes from the mailer-daemon return address is sent because of a failure in the original message sent by the user.
Specifically, the mailer-daemon is software stored in email servers that automatically delivers messages. The software goes through all email sent throughout the internet. Users are not contacted by the mailer-daemon software if there are no problems with any messages. The software exists to ensure the messages are properly addressed and sent, and only sends out its reply messages to users who have attempted to send a message that has an inherent problem.
The mailer-daemon informs senders of a failure in an email message that prevents it from being delivered to its original destination. This failure could be the result of a problem with the email address typed into the “to” section, such as a misspelling or a mistake. Another failure could be the result of a server problem with the email account, which should be fixed automatically in a matter of time.
The most common reasons for mailer-daemon alert messages are the account the message is addressed to does not exist, or the server – the information listed after @ – does not exist. Most of the time, problems that cause a mailer-daemon message are harmless and relatively easy to fix.
However, a message from mailer-daemon software may be an important sign that the recipients computer has been infected by malware that is using it as a launch point for spam email messages.
A common reason for the mailer-daemon message is the account that sent the message has been blacklisted by the receiving company. The mailer-daemon sets up the blacklist from email accounts that have sent an alarming amount of spam messages. Because certain types of malware infect computers and automatically send spam messages from users’ email addresses, an email account could be sending bulk messages without its registered account owner knowing about them. The mailer-daemon does not acknowledge the malware that causes the spam messages because it is designed to keep problem messages out of its respective server, simply sending the spam message back.
Email users who regularly receive messages from mailer-daemon software from multiple sources may be infected by malware. Certain worms and viruses infect computers and copy their victims’ email account information, using them later as sending addresses for spam attacks. As the account information is copied, and the spam messages are sent from a remote location, users may have a difficult time locating the virus and finding out their email address was used to send bulk messages.
To determine why they are receiving constant mailer-daemon messages, users should run a scan of their computer for malware. Regular computer scans can be important to detecting malware some users may not know about. Locating and removing a virus through a computer scan can eliminate mailer-daemon messages, as the software that was sending spam from the user’s email account is removed altogether. You can find more information about protecting your computer from attacks on the Ascentive website, or visit Clutter Free PC for software assistance.
Also, installing a protective software to prevent malware infections can eliminate the threat of malicious software from affecting users’ email accounts.
While the first steps to solving the mailer-daemon issue should be to check the accuracy of the recipient and server of sent email messages, scanning for malware could be a solution to prevent regular mailer-daemon messages.