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Reference

Email Campaign Rate Limiter: Overview, Configuration, and Troubleshooting Guide

Table of Contents​

  1. Overview

  2. How the Rate Limiter Works

  3. Configuration Reference

  4. Time Window Configuration

  5. Expected Send Pace

  6. Campaign Rate Limits

  7. Reading Campaign Analytics

  8. Troubleshooting

Overview​

The Rate Limiter is a campaign step that controls how quickly customers move through an email campaign. It is used to protect sender reputation during list warm-up, prevent sudden spikes that trigger spam filters, and stay within account-level sending quotas.

A Rate Limiter step holds customers in a queue and releases them in batches at a configured interval. Customers do not receive any emails while waiting at a Rate Limiter step — they simply queue until the next release window opens.

How the Rate Limiter Works​

When a campaign includes a Rate Limiter step, customers enter the campaign and immediately queue at that step. The rate limiter then releases a defined number of customers at each interval, advancing them to the next step (typically an email send step).

Example: A rate limiter set to 100 customers every hour releases 100 customers at the top of each hour. Those 100 customers then proceed to the next campaign step (an email send step, a wait step, etc.). The remaining customers stay queued until the next interval.

The total number of customers waiting at the rate limiter is shown as "X Waiting" on the campaign canvas.

LimitScopeDescription
Campaign HourlyPer campaignMaximum emails sent per hour for this specific campaign. Set by your plan tier.
Account HourlyAll campaignsMaximum emails sent per hour across all campaigns and flows in your account.
Account DailyAll campaignsMaximum emails sent per day across your account.
Account MonthlyAll campaignsMaximum emails sent per month. Tied to your sending quota.

The counters reset at the end of each period. If the account hourly or daily limit is reached, no further emails send until the counter resets — even if the campaign rate limiter would otherwise release customers.

Use the "Reset Rate Limits" button (visible in the Campaign Rate Limits panel) to clear campaign-level rate limit counters if needed during testing.

Reading Campaign Analytics​

Campaign analytics are available in two places:

Campaign detail view (right-hand panel)

  • Campaign Analytics (all-time): Total emails sent, delivered, opened, clicked, converted, unsubscribed, marked as spam, revenue, and calculated rates. These are all-time totals since the campaign was created or last reset.

  • Campaign Rate Limits: Current-period usage against each rate limit bucket.

  • Show Step Analytics: Toggle this on to see per-step breakdowns. Each campaign step displays delivery rate, open rate, click rate, conversion rate, sent/delivered/opened/clicked counts, spam count, and unsubscribed count for customers who passed through that step.

  • Time filter: Use the dropdown (e.g., "Last day," "Last 5 days") to filter step analytics to a recent period.

Communication dashboard (StoreFronts > Communication)

  • Email Sending section: Shows your monthly sending quota, quota used, emails sent, and emails remaining.

  • Customers section: Shows your active customer limit, current active count, and total customers in your account.

  • Performance section: Shows open rate, click rate, and revenue across all campaigns and flows for the selected period. The Flows table lists each active flow with its status and revenue.

Troubleshooting​

Customers are queued but no emails are sending​

Symptoms: The Rate Limiter step shows a large number waiting; the Campaign Analytics panel shows few or no emails sent in the current period.

Root Cause: One or more of the following conditions is preventing release.

Diagnosis: Check in order:

  1. Confirm the rate limiter step is Enabled (not toggled off).

  2. Confirm the rate limiter step is not Paused.

  3. If "Only release between" is enabled, confirm the current time falls within the configured window. Check that the end time AM/PM is set correctly.

  4. Check the Account Hourly and Account Daily rate limit counters. If either is at its maximum, emails will not send until the counter resets.

  5. Confirm the campaign is not in a Scheduled state that has not yet activated.

Solution: Correct whichever condition is blocking release. For the time window, edit the rate limiter step, adjust the end time AM/PM if needed, and save.

The campaign is sending, but much slower than expected​

Symptoms: Emails are going out, but the pace seems lower than the batch size and interval would imply.

Root Cause: The account-level hourly or daily limit is lower than the campaign rate limiter's batch size, or the active window is shorter than expected.

Diagnosis:

  1. Compare the Account Hourly limit against the rate limiter batch size. The effective rate is whichever is lower.

  2. Count the active window hours per day and recalculate expected daily volume using the formula in Expected Send Pace.

Solution: Adjust the rate limiter batch size to align with account-level limits, or upgrade your plan to increase account-level limits.

Customer quota is at 100%​

Symptoms: The Communication dashboard shows Customers at 100% quota used. A banner reads "Customer limit reached."

Root Cause: Your plan's active customer cap has been reached. UltraCart limits the number of customers active in your account at one time.

Diagnosis: Check Current Active vs. Max Active in the Customers section of the Communication dashboard. If they are equal, the cap is reached.

Solution: Upgrade your plan to increase the active customer limit. This does not affect in-progress email sends to customers already in the system, but new customers added beyond the cap may not be activatable without a plan change.

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