Performance observations:
Gmail seems to timeout after 9-10 seconds if the email is not sent successfully (thus the 12 second timeout in the Do-More SMTP config)
The transaction seems to take 1.85-1.90s of CPU time regardless of time slice (CPU fraction dedicated to the EMAIL). Total CPU time is very consistent across a range of CPU fraction from just over 20% to 65% which was the highest we tested, so it looks like the process is bound by the Do-More and there's no time spent waiting on Gmail at these transaction times. Internet bandwidth shouldn't be critical If we're Do-More bound for speed, but while I was testing this I had 10.8 Mbps down, 2.2 up.
The EMAIL needs a minimum of 21% of CPU time in order to allocate 1.90s of CPU time before the Gmail timeout, so for a 1666us TLS time slice, the average scan time while not emailing needs to be under 6.2ms.