While reviewing your Email notice failures, you may run across a number of reasons or codes behind the failure. The list below covers some of the most common errors you may run into.


  • Bounced Address
    This means typically that MessageBee has had a prior hard failure (bad address), and so generally won't try it again.  This helps to ensure that mail systems don't see MessageBee and the library as senders of spam due to repeatedly sending mail to a known bad address.  If you see this and the patron indicates it is a valid address, please notify Unique and we will work to ensure delivery. 

  • Spam Reporting Address
    This delivery error occurs when an individual marks a MessageBee communication email as spam from their email inbox. They may do this on purpose because they're not familiar with MessageBee communications and think it's spam, or they may do it accidentally. Check out the "Communications Preference" page in MessageBee to search for the address in question and verify if they have opted out of email communications. 


  • Unable to get mc info: failed to get IPs from PTR record: lookup <nil>: unrecognized address.
    This error is most often related to a typo or misconfiguration of the destination emails domain address (everything that comes after the (@ symbol). Most often is resolved by checking the email for typos and ensuring the right domain type (e.g. .com vs .org) is being used.

  • Unsubscribed Address
    This error indicates that the email address is currently suppressed by our system from further delivery attempts. At some point, the recipient indicated that they no longer wished to receive emails, and unsubscribed from your mailing list. Check out the "Communications Preference" page in MessageBee to search for the address in question and verify if they have opted out of email communications.  


  • Error Dialing Remote Address
    Indicates an issue with the recipients email server and we were unable to connect. Most commonly this means the domain name of the email address is invalid.

  • Unable to Parse Reason from Bounce Report
    MessageBee has encountered a previously undiscovered error message.

  • Invalid
    You can receive this error due to several reasons: You may have an invalid recipient's address, misspelled the address, or it simply does not exist 

  • Invalid Domain
    This error is most commonly related to mistyping or mis-entering a domain name for the destination email address.

  • Blocked
    This error is a 550 error that indicates a destination email server has flagged the email as SPAM and is blocking your communications.

  • Message Delivery Failed
    This error is a 550 error that indicates a destination email server has flagged the email as SPAM and is blocking your communications.

  • 450 
    The message failed because the recipient's mailbox was unavailable, perhaps because it was locked or was not routable at the time. 

  • 451
    The message simply failed, usually due to a server error. 

  • 550 
    The user’s mailbox was unavailable. Usually because it could not be found, or because of incoming policy reasons.


  • 551
    The intended mailbox does not exist on the destination server.  

  • 552
    The recipients mailbox has exceeded its storage limits.  

  • 553
    The message was refused because the mailbox name is either malformed or does not exist.

  • 554
    SMTP error 554 indicates that the mail server did not accept the email
    . Several reasons typically cause this error: Invalid Recipient Address - There are invalid recipient email addresses; in rare cases, the recipient email address may have been suspended or disabled.