Please note that GMAIL access is a moving target. These settings and guides work as per the date of this bulletin but may not be applicable in the future.
SMTP Host (or IP): smtp.googlemail.com
SMTP Authentication: Unticked
SMTP Account: Your gmail account. E.g., firstname.lastname@example.org
SMTP Password: Your GMAIL password
Your Email Address: Same as SMTP Account.
Reply To: Same as SMTP Account.
Furthermore, you must ensure that 2 Step Verification
is deactivated. Within your GMAIL account, open account settings, go to 'Accounts & Import' and then find and click on Other Google Account Settings
Finally, also locate Less Secure Apps
and ensure this is set to 'On'.
If email is still rejected, reset your GMAIL password and try again.