gmail will most likely block it in one form or another due to security restrictions. Locking down SMTP is a common way to block spam attacks.
For complete SMTP control, you can try to setup your own web server that supports SMTP. This way you can completely control SMTP security at the highest level. Web hosting is pretty cheap these days.
You might also want to chat with companies that provide email plugins. 360works cloudmail comes to mind for something that may integrate well for you:
I use my gmail account on more than one device at different locations.
You might need an app password. You would use the app password in place of your normal password.