I cannot use send grid to send email from a webserver that is in a private subnet.

The webserver is behind a load balancer for ingress and requires a proxy (allowed hosts list) for egress.

This workload must be compliant, so best practices in security are required. This network topology is baseline standard (but more commonly users will leave everything ooen and exposed) for the basics to meet compliance for CIS, PCI, IRAP, ISM, SOC2, ISO27018

This lib can be removed as redundant from my observation.
I suggest sendgrid use urllib to do HTTP instead of reinvent the wheel. if you need more features use requests instead of reinvent the aircraft.
Both of these options allow a per-request proxy setting AND most importantly they both respect the operating system proxy setting (on linux it is the env var http_proxy and https_proxy case insensitive).

I would appreciate some attention on this. thank you