Hi @Brad Lamont ,
Thanks for posting in our Q&A forum.
According to the error code, one article I found suggests that this issue occurs because the DNS service cannot be used if the Register this connection’s addresses in DNS check box is not selected in an Exchange Server 2016 or Exchange Server 2013 environment. Reference: https://learn.microsoft.com/en-us/exchange/troubleshoot/mailflow/dns-query-failed-error-when-email-stuck-in-draft
Another article suggests that if Exchange 2019 was installed into an existing site and the SCP was temporarily moved to Exchange 2013 or set to NULL, it needs to be updated. Depending on your configuration, you should point the SCP to either the internal FQDN of the Exchange 2019 server or to your load balanced namespace. Reference: https://techcommunity.microsoft.com/t5/exchange-team-blog/best-practices-for-migrating-from-exchange-server-2013-to/ba-p/3773084
Hope the above can help!
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.