What happens when I get an unroutable address error when trying to send an email?

Email delivery failures are a common challenge, and one frequent cause is the “unroutable address” error. This error occurs when the sending mail server cannot determine where to send your email.

When an email is sent, the sending mail server checks the Domain Name System (DNS) for the recipient’s domain. It looks specifically for the Mail Exchange (MX) record, which tells it which mail server is responsible for receiving messages for that domain. If no MX record is found that's when the below error occurs, as it's not possible to find a route to deliver the message.  

From: Mail Delivery System <Mailer-Daemon@relay1.stackmail.com>  
Sent: 12 May 2025 13:37 To: info@example.com Subject: Mail delivery failed: returning message to sender  
This message was created automatically by mail delivery software.  
A message that you sent could not be delivered to one or more of its recipients. This is a permanent error. 
The following address(es) failed: joe@bloggs.com Unrouteable address

What are the most common causes for the unroutable address error?

• The email address is incorrect or misspelt.
• The mailbox / domain is no longer active 
• The Domains MX records are missing or misconfigured
• The DNS lookup failed due to network or configuration issues

What should I do if I encounter the unroutable address error? 

The first thing to do is verify the email address you are trying to send to is entered correctly without any spelling mistakes or any typing errors. Once you've confirmed the email address is correct you should then make sure the domain you are sending to has a valid MX record. If after this you continue to have issues, it may be worth contacting your email provider to see if they are having any email related issues.