Instead of your Gmails Password, use the App Password instead when configuring your Gmail SMTP
An App password is a 16-digit passcode that gives an app or device permission to access your Google Account.
If you use 2-Step-Verification and are seeing a “password incorrect” or "Cannot connect to SMTP Server" error when trying to access your Google Account, an App password may solve the problem.
Most of the time, you’ll only have to enter an App password once per app or device, so don’t worry about memorizing it.
How to generate an App password?
Visit your App password page. You may be asked to sign in to your Google Account.
Select your Gmail account
Sign in to your account
(App passwords let you sign in to your Google Account from apps on devices that don't support 2-Step Verification. You'll only need to enter it once so you don't need to remember it.)
Select the app and device you want to generate the app password for
App Should be Other (Custom name)
Mention the Name of the App for reference
Click on Generate
Copy the password generated
Now that your password is generated, you can use it to sign in inside MMIO SMTP Email account settings
Once the password is generated you should receive a confirmation email