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How to fix Mail Delivery Subsystem: Your message wasn’t delivered

Emails have become commonplace and are the standard method for formal communication. Chat messengers are great for casual conversations but when something needs to be in writing, it’s put into writing in the form of an email that can be sent, CC’d and BCC’d to everyone involved. Some of the most popular emails services are free; Google and Microsoft both offer free accounts as well as paid business accounts. Sending, or receiving an email takes little more than a browser and knowing how to compose and send one.

Mail Delivery Subsystem

Mail Delivery Subsystem emails

Email is automated in lots of ways; users set up Out of Office messages for when they are away and not attending to emails, signatures, rules for sorting emails, forwarding addresses, and create block lists to keep unwanted messages out of their inbox. 

Emails from Mail Delivery Subsystem are automated emails sent when a message bounces. A bounced message is a message that was sent but not delivered. A message send failure usually happens within minutes of sending the message. In some cases, depending on the email address you’ve sent the message to, the delivery failure may take a few hours to arrive.

Fix Mail Delivery Subsystem: Your message wasn’t delivered

If you receive an email from Mail Delivery Subsystem, an email that you sent failed to deliver. This normally only happens with a single email. To fix this, you need to first determine which email the message bounced from. To find out, open the email from Mail Delivery Subsystem. It will tell you which email the messaged bounced from. The email may also tell you why the message bounced. 

An email may bounce for the following reasons and these problems almost all require the owner of the email to fix the problem.

Inbox is full

Email inboxes seem to be infinite and that may seem true if your inbox is 10GB or 15GB in size however, that is still a finite amount of storage. Once the storage space runs out, the email account will not be able to receive any more messages until space is freed up. 

If your emails to a particular account keep bouncing, it may point to the recipient’s inbox being full. Ask them to clean it up and free some space for new messages.

Email is inactive/suspended

Email accounts can be deleted. Users can manually delete their emails.  Email accounts can be suspended if they are found to be violating the terms of service of the domain they’re on. If the email is a business email, the account can be suspended if the subscription expires. 

This sort of problem normally manifests in the form of an email not found message that accompanies the Mail Delivery Subsystem: Your message wasn’t delivered email. Again, you will have to reach out to the recipient through a different mode of communication (or a different email), and ask them to fix it.

Incorrect email

If you send an email to an account that does not exist i.e, you’ve entered an incorrect email address, the message will bounce. Much like sending a letter to an address that isn’t real, the message delivery will fail. Check and make sure you’re using the right email. You may have the wrong domain or there may be a typo in the address that you’ve typed. 


Mail Delivery Subsystem tells you your message didn’t deliver. It may, or may not tell you why the delivery failed. The message may also be accompanied by an error code or it may include a response from the server the email was sent to. You can look up the server response to see why the message delivery failed. 


  1. 10/21/22
    I received an email titled Mail Delivery Subsystem saying that I can no longer send emails because I exceeded my limit! What can I do to allow me to continue to send emails?
    Many Thanks,
    Gary Leigh
    (313) 690-8747

  2. Please use this email to post our daily mail delivery. Another email was used
    612 tomahawk dr. Kingsport TN 37664

    The Bullard’s

  3. With regards to that issue…how can I recover my attachments suppose I sent the email earlier with attachments?

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