Thank you for your message.
Could you please double-check if you have the less secure apps access
feature enabled in the Gmail settings? For more information on how to enable it please, refer to this Google Account Help Center page: https://support.google.com/accounts/answer/6010255?hl=en&authuser=1
If enabling the less secure apps access feature doesn't help to resolve the issue, then we recommend that you try another SMTP provider. For example, please consider using services like Mailjet
which is convenient for the purpose of setting up the SMTP server in case if you need to be sending a relatively small amount of emails.
In order to start using it just sign up using any email address (you might even use the Gmail email address you've created). After creating your account you're able to see the SMTP settings right away, so you can copy the SMTP settings provided by the service to the MSI configurator.
However, please note that Mailjet applies a sending limit of 10 emails per hour for free accounts. You can learn more about the limitation here
In addition, please note that our MSI Configurator tool only provides an interface to embed the SMTP server data. Unfortunately, the MSI Configurator cannot control how the SMTP server works and it doesn't perform the actual sending - the SMTP server does.
Please let me know if the solution above worked for you.