As this seems to be a different issue than the resolved post I was commenting on and I have new information I am posting here.
When I configure to send via any digest timeframe mails are not sent. Not the digest and not the <send email preview> regardless if there is a recent post. When I switch to the "For each post" selection the mails go out as expected and the preview mails go out as well.
I originally was running this on godaddy servers and researched and made sure I was configured as suggested and the From emails were from the home domain and were active email accounts. I tried with the same results via email() and SMTP (Linux host). I also tried number of recipients at 0, 1, 10 and 30.
In each case emails went out if the plugin was set for posts, but not for digest (incl previews).
SO... I migrated to my VPS Liquid Web box and got the exact same result. I'm now going to do a clean install and see what the end result is.
What is bugging me most is that it works so well for post notification. Could the Cron be screwed-up? on both Godaddy and default Liquid Web VPS host?
thoughts... ideas? I'd even take a smart remark at this point.