Nothing is displayed on the sidebar.

Multiple people are now logged in to the browser, which is the root cause of this error message. Simply log out with all users besides the one you’ll be using to utilize the add-on. Alternately, you can use the incognito mode or a different browser.

How many Email messages can I send per day?

Our application is completely free but has limitations set by Google. Gmail users can send emails up to 100 recipients per day while the daily limit for GSuite (Google Workspace) accounts is 1500 recipients per day. For more details Visit and see “Email recipients per day”: https://developers.google.com/apps-script/guides/services/quotas

How could I increase daily quota for sending mail?

You could increase your daily quota by creating Google Workspace account. You will require to subscribe to at least “Business Starter” edition. Please visit https://workspace.google.com/intl/en_ie/pricing.html