Gmail as SMTP Server on Appian 18.3

Hi,

I have just installed a new Appian Server 18.3 on a Windows 2016 Server but I could not make work GMAIL (on TLS) as SMTP Server.

By launching a simple process with a sendMail smart service the tomcat log says:

I configured custom.properties and password.properties with USER and PASSWORD by following documentation, with these parameters: 

custom.properties:

conf.mailhandler.mail.smtp.host=smtp.gmail.com:587
conf.mailhandler.mail.smtp.auth=true
conf.mailhandler.mail.user=myaccount@gmail.com

conf.mailhandler.mail.smtp.starttls.enable=true

conf.mailhandler.mail.smtp.starttls.required=false

password.properties:
conf.password.SMTP=mygmail.password

If I try to connect from the command prompt on the server with telnet smtp.gmail.com 587 it appears successfully connected

And finally, we have another Appian Server version 17.2 on Ubuntu with the same configuration on same network but it works perfectly.

Can you help me?

Thanks!