Enhanced Google security sometimes sees Method IP addresses as unsecure (which they are not), so Google won't let some users set their email preferences.
If you have experienced this problem, you will have received an email from Google saying:
sign in attempt blocked or
someone has your password
To fix this problem, you should
Enable 2-Step Verification
In Gmail, open your account settings by clicking your profile icon at the top right and then click the button Manage your Google Account.
In your account, on the left menu, click Security.
Scroll down to How you sign in to Google, and click 2-Step Verification.
You will be taken through a series of screens to enable 2-Step Verification. You will need to verify it is you by entering your password.
Generate an App Password
Once 2-Step Verification is enabled, you will able to generate an App Password. This is only available once 2-Step Verification is enabled.
Still within the Security tab, under How you sign in to Google, click 2-Step Verification.
Scroll to the bottom of the 2-Step Verification page, and click the arrow for App Passwords.
Click Select app and then choose Other (Custom name) from the dropdown list.
Type in a name for the app. In the below example, we used "Method". Click Generate.
You will then be given the password key for this app as highlighted in dark yellow below. Screenshot or store this in a safe place as this is not stored anywhere. Go back to Method and paste in this password in the Gmail server settings for the email password.
And that's it! You're done!