What is Mail Delivery Failed: Returning Message to Sender Bounce-Back?

Usually, emails get successfully delivered to their recipients, but this is not always the case. Every once in a while, mail delivery can fail. The reasons can be several including the email being blocked due to spam content, invalid recipient address, wrong email server issues, etc. In such instances, the sender is usually notified via an automatic bounce-back message generated by the mail delivery server, thus letting the sender know that the email has not been delivered to its destination.

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What is Mail Delivery Failed?

The bounce-back email received in case of an email delivery failure will contain information about what happened, and it will include the reason for the bounce-back as well as the body of the original message you were trying to send. Usually, when mail delivery fails, depending on the reason of the failure a variation of the “Mail delivery failed: returning message to sender” or a “554 Denied” error will appear in the subject line of the bounce-back message.

The 554 email error is sometimes viewed as a generic, catchall phrase for email errors that aren’t specifically defined by other email error codes. Mail Delivery Failed: returning message to sender bounce-backs are typically hard bounces, meaning that attempting to re-send the message will not be successful. The situations described below are some of the most common reasons for a mail delivery failure and 554 error bounce-back messages being returned by the mail delivery server.

Common Causes for Mail Delivery Failed Messages and How to Resolve Them

The most common reasons for a 554 Denied email error are sending emails with spam content, invalid recipients, virus detection issue, improper email forwarding causing mail loop, etc.

Sending Mail With Spam Content

If your email contains spam words, the email service provider will flag it accordingly and reject it. You need to examine your email for any spam content that it may have, and make changes to the email. You can try sending it once again from a different email account to see if the problem persists. If your email bounces back, try contacting your web hosting company who can help to shed light on the issue. Make sure you include all necessary information, that is, the sender email address, recipient email address, the bounce-back message in full, including the subject line. Alternatively, you can ask the intended recipient of the email to whitelist your email address.

Another reason why your email is flagged as spam might be that the previous owner used the IP address for sending out spam. It is a good idea to check you IP reputation or if your IP address is listed in several Spam databases, for example Spamhaus.

Blacklisting

Sending out too many spam emails can also cause email bounce-back problems. If your IP/domain or email address is blacklisted for spamming, you may encounter message delivery failures. Sometimes, blocks may be placed by your web hosting company simply for large volumes of email being sent out from your domain/host. In case of blacklisting, you need to contact your web hosting provider who will want to have themselves removed from the blacklist. When the block is placed by your hosting provider for suspiciously large volumes of emails sent from your domain, the hosting company will require you to comply with certain requirements before it can lift the ban. Generally, you can’t just buy a hosting or email service and start sending out hundreds of thousands of emails. First, you will be given a limit, let’s say 1000 emails per day. If you use that limit and very few people send spam reports, then your host might increase the limit slowly. This is the practice for example at Amazon SES (Simple Email Service).

Wrong Email Server

Another issue that could cause a 554 email error is a misconfiguration error with the receiving domain, the result being that a domain may not accept emails from that domain’s users, or an error with the sender’s system because the host may be using the wrong email server to send out the email, which results in the outgoing email server not recognizing the domain of the sender’s email address.

The error can also appear when changing hosting providers and while the change is still underway, your message may reach the old hosting provider that no longer accepts mail for the domain that was transferred. Re-sending the email after the domain propagation has taken effect will result in a successful delivery.

Also Read: Best Gmail Alternatives for Personal and Business Emails

Invalid Recipient Email Addresses / User Unknown

Another scenario that will return a bounce-back message is when too many emails are sent to invalid recipient addresses. This user unknown bounce-back can be caused either by email addresses that have a type in the username or domain, or because the email address no longer exists on account of it being shut down for example. Check the email address for typos and try to contact the person you’re trying to send an email to and see if the email address still exists or whether the problem is on the recipient’s end.

If you run a mailing list with subscribers that bounce email due to this error, make sure to remove them from your list.

Improper Email Forwarding Causing Mail Loop

This scenario appears when a user has two accounts that forward to each other, thus creating a back and forth between the accounts. This loop is eventually ascertained and a “554 Too many hops” error message is returned to the sender.

Virus Detection

If you receive a bounce-back message, which states the reason for the rejection as “554 Rejected Due To Virus”, it means that some malware may have taken a hold of your PC. The malware responsible for this is most likely a Trojan virus, and you’ll have to remove it from your system to make the problem go away.

Also Read: How to Build a Website and Get Free Business Email?

Conclusion

Mail Delivery Failed: returning message to sender bounce-backs can be caused by a variety of issues, the ones elaborated above being the most common. Some web hosting providers have so-called bounce-back email parser tools that can help you easily identify and troubleshoot the problem by copying the bounce back email in an input box that will analyze it and offer solutions to resolve the problem. Of all the possible causes, spamming related blacklisting is probably the most common reason.