No DNS changes were made in recent builds because DNS has been massively changed with our .NET 7 release.  

I would look at your network and/or DNS servers as the source of your problem. 

DNS 8.8.8.8 & 8.8.4.4

Nothing esle has changed except Updated to 8664. Should we be on net 7.

The spike in times are related to DNS, Network or some other issue on your server that is causing delays.  If you would like us to help diagnose, you can contact support.  

The .NET 7 release improves accuracy of DNS results as there were times the previous .NET Framework would cache previous results.

Repaired net 4.8 seemed to fix the issue..

We have been experiencing the same thing for a number of weeks with other issues related to this cropping up. We already have a support ticket open, and their "solution" was to upgrade to the BETA, which we definitely will not be doing.

I am sure that smartertools will not release any additional updates to the current version.

You will have to wait for the next version of smarter mail in .net 7