Unroutable domain error message
When sending emails you may occasionally encounter the following type of message:
"550 unroutable domain: [domain]"
This error message essentially means that the domain name of the email address you tried to send an email to doesn't have a valid MX record. An MX record is the mailbox for a domain name, where emails for that domain name should be delivered.
So, if you tried to send an email to email@example.com then either baddomain123.com doesn't have any MX record(s), or its MX record(s) are not reachable for some reason.
You can find out what the MX records are (if they exist) by searching on this site:
If no MX records exist, you should double-check to make sure you haven't made a spelling mistake.
If MX records do exist, you can try pinging them or running a quick telnet test (on port 25) to the MX record with the lowest-numbered priority.
Alternatively, get in touch with us, and we'll look into the situation.
You may need to contact your recipient by other means if you need to contact them quickly.