I’ve just built a new computer and have been setting up all my software on it again, as part of that I need to set up Calibre to download news and send it to my Kindle via my Gmail account.
The first thing to take care of is whitelisting the email address you plan to send documents to your Kindle from, this can be done in the “Manage your Devices” page as explained here.
Once that’s been done you need to create an app password in your Gmail account to allow Calibre to send emails, this can be done here by adding a new device and copying the generated password for use later. If you can’t see the Security > Signing in to Google > App passwords section and the above link doesn’t work then you’ll need to enable 2-Step verification if you haven’t already (thanks Meghan).
Once that’s been done Calibre can be set up to send via Gmail in the “Sharing books by email” section of the preferences.
Send email from: Your gmail address
Username: Your gmail address
Password: Your app password
Send yourself a test email and hopefully it’ll arrive!