I created a member list for people that logged in after 01/01/2020 in the cp.
You could send a email from that.
It is not that large
Just one page
Just select the saved search login after 01/01/2020 scroll to the bottom select email for action.
Then all from search.
On the next screen add your content and send
There is also a test email in that page where you can send just one email to yourself for a test.
I am trying to remember the limit from the host but I am thinking 30 per hour so You need to keep your browser on that page for the duration.
You can still open another browser window to visit the site.

There is no such thing as stupid questions , Just stupid answers.