This issue seems to be related to your Gmail account and not the Email Connector module.
The error states that you need an application specific password.
Follow this instruction to set up an app password and use that one to configure the email connector module.
I hope this helps
Hi,
Gmail no longer supports basic authentication (user names and passwords), but you may still be able to set up an account in the Email connector. Please follow these instructions to move ahead on this.
https://docs.mendix.com/appstore/modules/email-connector/#gmail-accounts