Almost all of us have received a mailer daemon message at one or more points in our lives. It is an indicative response generated if an email fails to get delivered. The mailer daemon message also has an attachment describing the reason for the delivery failure.
We'll explore the answers to all these questions and discuss all that you should know about mailer daemon. Let’s dive in.
What is mailer daemon?
Mailer daemon automates the management of undeliverable emails, sending failure reports to the sender's inbox with explanations. It retries delivery for days and sends a final report. This tool keeps users informed on the delivery status of emails, aiding effective communication.
When it fails to deliver the message to the destined inbox, it sends a message to your inbox stating the failure and its cause. Usually, these messages come from an address that looks like this - mailer-daemon@xyzcompany.com. Here is how a message from mail delivery subsystem looks like.
Why is mailer daemon important?
Mailer daemon helps you in the following ways:
Usually, a mailer daemon error report, or failure message, allows you to know the cause for email delivery failure via the mailer daemon attachment.
When you know that some of your emails were rejected, along with the reason behind this rejection, you can address the exact issue and ensure email deliverability.
Further, if you are getting these messages, even when you have not originally sent the message, then it indicates that you are a victim of spamming.
However, there can be another unwanted event triggered because of the entire scenario - mailer daemon permanent error. This means you are not able to send any emails.
Frustrating, right?
This is a result of a virus infection or a password breach that allowed some spammers for a continuous spam blast. The mailbox provider can automatically shut down the “send” function until the entire situation is resolved. The “send” function is restored once the device is scanned, the virus is removed, the password is changed, and the mailbox admin is sure that no spamming occurs again.
Take a look at the mailer daemon message example shared below.
Source
The reason for email delivery failure is mentioned in the mailer daemon attachment and might or might not require technical handling on your side.
But, then again, why are you receiving such emails, to begin with?
Escape the spam folder with managed deliverability
Why do you receive mailer daemon emails?
When you send an email message, it is verified by the mailer daemon server. You receive these emails as a result of sending an email to an account that:
No longer exists because of domain change or termination of an employee.
Is misspelled, or typed wrongly, and
Allows only whitelisted email addresses to send messages.
Hence, mailer daemon message is a useful tool to tackle the problem of undelivered messages and to figure out if anything fishy is happening with your email, such as email phishing, etc.
What should you do when you receive an email from mailer daemon?
If you get a mailer daemon message for an email that you sent, then you must open the attachment and check the reason for the failed delivery.
Based on this reason, you can take any of the following actions depending on the reason:
Check the email ID for spelling mistakes.
Contact the person via some other medium, such as a call, to learn more about the error in email delivery.
Contact someone at the organization to whitelist your email address and let the messages pass through.
Email error codes and their meanings
Email error codes hold critical information about delivery failures. These codes help pinpoint why an email wasn't successfully delivered, ranging from a simple typo in the recipient address to more severe issues like unauthorized access.
| Error Code | Description |
|---|---|
| 400 | Bad Request - The server could not understand the request due to invalid syntax. |
| 401 | Unauthorized - Authentication is required and has failed or has not been provided. |
| 403 | Forbidden - The request was valid, but the server is refusing action. |
| 404 | Not Found - The requested resource could not be found. |
| 500 | Internal Server Error - The server has encountered a situation it doesn't know how to handle. |
| 502 | Bad Gateway - The server was acting as a gateway or proxy and received an invalid response from the upstream server. |
| 503 | Service Unavailable - The server is not ready to handle the request, often due to being overloaded or down for maintenance. |
| 550 | Requested action not taken: mailbox unavailable - The recipient's mailbox cannot be found or is unavailable. |
| 551 | User not local - The recipient is not local to the server. The server needs to forward the request to a different server. |
| 552 | Requested mail action aborted: exceeded storage allocation - The recipient's mailbox has exceeded its storage limit. |
| 554 | Transaction failed - The email transaction failed for unspecified reasons. |
Understanding bounced messages
Bounce messages are automated replies generated by mail servers when an email fails to deliver to its intended recipient. These messages inform the sender of the failure and typically include specific error codes and descriptions detailing the reason for the bounce. Bounce messages are categorized into two main types based on the error codes:
Soft bounces (400 Series): These indicate temporary issues that prevent delivery. Common reasons include a full mailbox (code 452), temporary server problems (code 421), or the message being too large. While soft bounces can resolve themselves, they signal that you should monitor the situation, as repeated soft bounces may affect your sender reputation.
Hard bounces (500 Series): These indicate permanent problems with email delivery. Examples include non-existent email addresses (code 550), unauthorized users (code 551), or incorrect domain names (code 554). Hard bounces require immediate action, such as verifying the recipient's email address or removing it from your contact list.
What is mailer daemon spam?
Mailer daemon spam is the endless list of mailer daemon failure notice email messages that reach your inbox because of the possibility that spammers have forged your email address or used your compromised email password for spam blast.
The spammers collect any email addresses they can find from all over the internet. But, the odds of these addresses being misspelled, wrong, invalid, deactivated, old, or even fake are extremely high. The spammers use any email address in their database to send a spam blast to these email IDs in their database. The mailer daemon generates an error message for each of the invalid addresses and sends them back to the sender.
Still, you are not a spammer, and you are still receiving these messages. Why?
This is because the spammers are highly likely to use any random email address instead of their “real” email address for a spam blast.
Malware and viruses can significantly impact email communication, often resulting in unwanted mailer daemon messages. If your email account is compromised by malware, spammers may send out bulk emails using your address, triggering bounce messages when those emails fail to deliver. This not only clutters your inbox but also damages your reputation as a sender.
This is called email phishing.
And if you receive mailer daemon message for an email that you didn’t send, then it’s highly probable that you could be a victim of such a phishing attack. While most mailer daemon spam subsides by itself after 2 or 4 days, it can continue, as discussed above.
Now, let us find out what to do in such an event and how to stop mailer daemon emails.
How to avoid mailer daemon spam in the future?
There are a few things you can do to tackle the current spam and similar issues in the future:
1. Scan and remove the mailer daemon virus
Scan your devices, laptop, mobiles, and desktop (whichever you are using for opening your email) using a reliable anti-virus program to detect any malware and get rid of it.
Use spam filters provided by your email service to catch suspicious emails. Be cautious of unsolicited messages requesting personal information, and never provide sensitive data without verifying the source.
2. Change your email password
Next, change your email password or seek assistance from your mailbox provider to help you do the same. Always ensure that you log in with the new password only after you have scanned and removed the virus. Otherwise, the virus can get your new password as soon as you key it in, and the process will continue.
Regularly updating your passwords and enabling two-factor authentication can also enhance your email security.
3. Notify your email contacts
It is important to point out that you might receive the mailer daemon messages for a few more days as the servers finish delivering the messages, but you can always delete them until they stop automatically. If you are a victim of mailer daemon spam, we recommend informing your mail contacts about the same and informing them about any suspicious activity initiated from your email address. Always remember, that every link in a virus chain is important!
Browse with caution - Your online activity is always under the scanner!
Paying attention to what pages you visit, what links you open, and what you download always ensures your safety from unwanted spam attacks. While you might be busy browsing, you can end up being prey to data snoopers, hackers, and spammers.
So, browse with caution, and don’t forget to check the mailer daemon attachment to know why you got the message in the first place!
