If your campaigns break in amplemarket with a user quota exceeded message, then you've hit a Gmail sending limit. Gmail sending limits can change without notice and limits per day are applied over a rolling 24-hour period, not a set time of day.
The reason most users hit their sending limit is because they are in a trial account, where the limit for sending emails is 500. You can see the entire list of Gmail limits here.
The easiest way to get out of this very low limit is to skip the trial period. Trial-like sending limits are removed when the two following requirements have been met:
- The account is no longer in trial and has started an active subscription.
- The account is cumulatively billed for at least $100 USD (or the same amount in local currency).
- At least 60 days has passed since reaching that payment threshold.
To end your trial and convert to a paid account, go to Set up paid G Suite service.