Problem statement
We are getting an email error for a specific domain called “example.com”.
When trying to send the authentication email, it’s giving the error “queryMx ESERVFAIL example.com”. I verified that the domain has MX records that are correctly set up and all of our emails to other destinations are reliably delivered.
What is the meaning of the error “queryMx ESERVFAIL ” and how can we fix this problem?
Symptoms
Attempting to send email to a specific domain ( e.g. example.com ) results in delivery failure.
If you look in the tenant logs, you will find one or more Failed Login ( fn ) events, together with a description that contains the string "queryMx ESERVFAIL ". Selecting and viewing one of these log events will provide more information about the specific problem.
Troubleshooting
You can check the health of the domain with a 3rd party service such as MXtoolbox: https://mxtoolbox.com/emailhealth
Note that these problems might sometimes be intermittent.
Solution
Auth0 is unable to offer any direct assistance with this matter. This is due due to the the fact that the problem is caused by DNS configuration issues that are outside of our control.
Only the domain administrators can fix these issues. If you have any other means to contact the recipient (e.g. phone) then you could ask them to investigate the problem on their side. This most likely would involve them contacting their email / DNS provider and asking them to perform a health check and perform remedial action.