If you have a free Gmail account and would like to use that account inside Kennel Connection to send emails, you'll need to make sure you do not have 2-Step Verification enabled. Please read below for instructions.
If you have a paid G Suite professional email account where it ends in @yourdomain.com, please see this article: Disabling 2-Step Verification in G Suite
Part 1. Gmail Inbox Settings:
Login to your Gmail email inbox. Once logged in, click your logo or photo or letter in the upper right hand corner and choose "Manage your Google Account"
Once inside the account settings, click on the security option on the left hand side:
Look for the 2-Step Verification setting. If it shows ON, you must click it and turn it off. If it shows OFF, you can close out of Gmail inbox as you are all set.
Changes will save automatically.