Postfix : TLS is required, but was not offered by host smtp.gmail.com

Dear All,

We need to make linux root send email for notifications, job status, cron results...etc. So we are trying to make basic and simple configuration to postfix with gmail as relay; all sent emails are in mail queue with:

TLS is required, but was not offered by host smtp.gmail.com[74.125.206.108])

How to solve this issue;

Thanks in Advance,

Shareef