Installing and upgrading help

Dear Sergio:

Thanks a lot for sharing this information. Using the link you shared I'm able to send mail from a Postfix server though a G Suite user account. The idea is to use the Postfix server to be used as an intermediare server between Moodle and Gmail. However, I cannot send mail from our Moodle server using the intermediate (Postfx) server. Checking the mail.log information of the Postfix server I get the following error: 

connect from (our moodle server domain name)

SSL_accept error from..(our moodle server domain name)

lost connection after STARTTLS from (our moodle server domain name)

disconnect from  (our moodle server domain name)

The /etc/postfix/main.cf has been configured using the parameters shown in the link you shared.

Could you share your Moodle's configuration of "Site Admin -> Server -> Outgoing mail configuration"?

Any idea or suggestion will be very much appreciated.