You can not use CDOSYS, but you can use Persists AspEmail with Gmail using STARTTLS.
No coding is required. All you need to do is from the 'Email Settings' page in the 'forum admin area' select the option for 'Persists AspEmail with TLS'.
After the connection is made to Gmails SMTP servers, Gmail will then send the STARTTLS command and Persists will then change to using TLS encryption for the connection.
I use this on several forums with Gmail and it works out the box with no code changes needed.
Edited by WebWiz-Bruce - 30 September 2019 at 12:16pm