Apologies if this is in the wrong forum, but I wanted to share with the community how I managed to get gMail up and running with CLAWS Mail on my Raspberry Pi3B+ (this method should work for other Pi's too).
It's a pretty easy one really. If your gMail account uses 2-step authentication, and so using your regular gMail Google password will fail when trying to conenct with CLAWS mail, so you will need to set up an app password within the Google settings on the email account you wish to set up on your Pi.
Simply set up a new device in Apps Passwords from the Signing in to Google section of Account Settings.
My Account > Sign-in and Security > App Passwords
Verify your current Google password, use the drop down for Select App, select Mail, then on the Select Device > Select Other - I made up a name for my Raspberry Pi - this is only for indicative purposes so you know by looking at your Google Account Settings page which apps you have set up a separate password for, then click the GENERATE button.
You will then be given a 16 digit password which you should note down and keep somewhere securely. Use this password in the CLAWS password area when setting up the gMail account in CLAWS -don't use your regular gMail password, as this will fail Googles authentication.
Also; it's best to use IMAP configuration.
Hope this helps.