What happens if you hit the Gmail sending limit?
If you hit the 24-hour Gmail sending limit, you may see a message that says “You have reached a limit for sending mail.”
In this scenario, Gmail puts a temporary hold on your ability to send emails to ensure fair usage and prevent spam.
You should be able to send emails again within 1 to 24 hours, depending on how many you sent at various times throughout the prior 24-hour period (see example above).
Source: https://www.streak.com/post/gmail-daily-sending-limit?utm_source=customerio&utm_medium=newsletter#hitting-the-limit