My Email Sending Limit is not 1500

I am using the Mail Merge with Attachments addon for sending emails via Google Sheets. My premium plan should allow me to send 1500 emails daily, but I am currently limited to sending 400 emails per day.

Why is my quota not 1500 in Gmail?

There could be several reasons by your email-sending quota is limited to 400 emails per day.

Reason 1. You may have activated the license on a free or account. Please note that Google offers a higher email quota to paid Google Workspace accounts only.

If you have a Google Workspace account, you may contact support and request a license transfer from Gmail to a Google Workspace account.

Reason 2. If you have a Google Workspace account and yet your quota is not 1500, it is likely that you have recently created a Workspace account with Google.

Google imposes the following restriction on new Workspace accounts.

When you sign-up for Google Workspace, your account starts a trial period and Google will increase your sending limit only after the trial period ends.

Your account will be removed from the trial mode when it has been cumulatively billed for at least USD 100 (or equivalent in your currency). This amount doesn’t include the cost to purchase your domain.

The other requirement is that at least 60 days have passed since you have reached that payment threshold.