allowing smtp access to gmail for a GSuite account

The (admin of the domain or user?) would need to do the following:

1. log on to your account

2. go to https://www.google.com/settings/security/lesssecureapps

3. turn the option from OFF to ON (allow less secure apps ON).

This is from

https://productforums.google.com/forum/#!msg/apps/Ik_NcksX9sA/8dzVfQyYEwAJ