I cannot get email notification to work

If you try this on a "clean install" OS, does it work?

(You can install easily by running Disk Utility, add a volume to your startup disk, then boot into internet recovery mode,and install OS X into the new volume) this will "Share" the space with your volume, so it is not a hard partition, it is an APFS soft partition.

Let me know if you get the same stall in sending the test message.

As I said, that's a lot of work.  Is there anything else we can do before I do that?

Just do it at night. It is pretty simple with APFS volumes. Create a volume inside your volume and internet recovery boot, install macOS into it. Its valuable as an emergency boot volume also.

This is what engineering needs to see before I can get attention on this.

thanks for understanding.

Also, that system is a very generic system.  mini 2018.  Your software is the only thing that has system level stuff in it.  The other stuff is on the application level (e.g., Chrome). It's just a file server.  So, I'm pretty sure the test is going to show the same thing.

Probably but I am trying to get engineering off SoftRAID 6 development to take a look at this, which means proving it is not happening on a clean install. Its part of my price to get the time. ;-)

Is there something akin to strace on Linux?  That is often very good at diagnosing problems like this.  I'm not as familiar with macOS, though, to know if something like it is available.

We do not have that command. We have debug builds we create on occasion, but email is a separate piece of code, we intend to rework the email code in SoftRAID 6, but Big Sur/ARM are higher on the list right now.