Mail blocked after 2 successful sends. VBA error -2147220973

I have a MS Access 2013 database application which generates e-mail messages via VBA/CDO to our clients.  When this is run on a machine that doesn't have NIS 2013 on it, it runs just fine and all of the e-mails go through.  When I run it on the production machine, which has NIS 2013 on it, it sends 2 messages and then I get error -2147220973 "The transport failed to connect to the server".

 

Note that I am connecting to smtp.google.com on port 465 with SSL.

 

How do I stop this behavior?

 

-- Geoff