Email throttling
Email throttling is a deliverability safeguard that temporarily reduces the rate at which survey email invitations are sent. It activates when a survey’s bounce rate exceeds acceptable levels.
Agile Research operates on a shared email infrastructure. When any single account sends a high volume of emails to invalid addresses or generates excessive spam complaints, it can affect email deliverability for all customers on the platform. Throttling protects the health of this shared infrastructure while giving you time to address the underlying issue.
Throttling does not stop email delivery entirely. Your survey remains live, respondents can still complete it, and you retain full access to results and contact data. Throttling only slows the rate of outgoing invitations until deliverability metrics improve.
How throttling works
Agile Research automatically monitors bounce rates for every live survey. These checks run every 15 minutes and evaluate recent activity using rolling time windows. Bounce rates are calculated based on the last two hours of email activity for the survey.
This evaluation happens automatically. No action is required from you unless a survey is flagged or throttled.
Throttling thresholds
Bounce rate thresholds determine when Agile Research takes action on a survey. These thresholds reflect industry standards enforced by major email providers and are designed to keep deliverability rates high for all customers.
The following are bounce rate thresholds:
At Risk (> 5% and < 10%) — When a survey bounce rate exceeds 5%, it is flagged as At Risk. At this stage, the survey may be throttled at any time based on overall platform conditions. This is not guaranteed; it serves as an early warning.
Throttled (> 10%) — When a survey bounce rate exceeds 10%, it is immediately throttled. The email send rate is reduced and will ramp back up as the bounce rate improves.
The following is a complaint rate threshold:
Warning (> 0.1%) — When a survey complaint rate exceeds 0.1%, the system sends a warning notification to the account administrator and the survey owner. This is a warning only; the survey is not immediately throttled. However, complaint rates that continue to rise will result in throttling.
| Metric | Threshold | Action |
|---|---|---|
| Bounce rate | > 5% and < 10% | Survey is marked At Risk and may be throttled. |
| Bounce rate | > 10% | Survey is immediately throttled. |
| Complaint rate | > 0.1% | Warning notification sent to admin and survey owner (no immediate throttle). |
Why bounce and complaint rates matter
Even outside of the Agile Research throttling system, high bounce and complaint rates have a direct impact on whether your survey invitations reach recipient inboxes. Understanding how email providers respond to these signals will help you see why contact list hygiene is so important.
How email providers respond to high bounce rates
When a large percentage of your emails bounce—they cannot be delivered because the address is invalid, non-existent, or unreachable—email providers like Google, Outlook, and Yahoo interpret this as a sign of poor list management and assume the sender may be using outdated or non-consented contact lists.
This triggers several consequences for your future sends:
Increased spam filtering. Email providers begin routing your messages to recipient spam folders, even for contacts who previously received your emails in their inbox.
Throttling by the provider. Some providers slow the rate at which they accept emails from your sending domain, delaying delivery even for valid recipients.
Domain blocking. If high bounce rates persist over multiple sends, providers may block emails from your domain entirely or add it to an internal blacklist.
How email providers respond to complaints
A complaint occurs when a recipient actively marks your email as spam or unwanted. The industry benchmark for complaint rates is generally below 0.1%. Even modest complaint rates above this threshold are a strong negative signal to email providers.
High complaint rates lead to:
Automatic spam routing. Once complaint rates cross a provider’s internal threshold, future emails from your domain are automatically directed to spam folders for most recipients.
Reputation downgrades. Providers use complaints to lower your sender reputation score in their systems. A low sender reputation drastically reduces the likelihood that any of your emails across all surveys reach the inbox.
The compounding effect
Bounce and complaint rates don’t just affect the current survey. They damage your sending domain reputation with email providers, which impacts deliverability across all future surveys sent from your account. As more emails land in spam, engagement rates (opens and clicks) drop, which reinforces the negative signal and makes it even harder to reach inboxes going forward.
Agile Research monitors these metrics and applies throttling proactively to catch deliverability problems early before they cause lasting damage to your sender reputation.
Email ramp-up rate
When throttling is applied to a survey, Agile Research reduces the email send rate and then gradually ramps it back up as deliverability metrics improve. The ramp-up works as follows:
Email batches are sent every 5 minutes.
Agile Research starts at a rate of 60 emails per hour (approximately 5 emails per 5-minute batch).
Every 15 minutes, the rate doubles: 60/hr → 120/hr → 240/hr → 480/hr → 960/hr, and so on.
This doubling continues until the survey reaches maximum deliverability.
Agile Research re-evaluates bounce and complaint rates every 15 minutes. If rates improve, the send rate increases automatically. No manual intervention is required.
For example, a survey with 100,000 pending invitations is throttled. Under the ramp-up schedule, in the first 15 minutes, approximately 15 emails are sent. In the next 15 minutes, approximately 30 are sent. The rate continues to double every 15 minutes. If bounce rates remain healthy, the survey can reach full send speed within a few hours.
Survey Deliverability page
The Survey Deliverability page gives account administrators a survey-level view of email deliverability health across all live surveys. Use this page to identify which surveys are experiencing issues and take corrective action.
Check the Reputation page regularly, especially after launching surveys to new or large contact lists. Surveys with elevated bounce or complaint rates will be easy to spot. Click a survey name to see detailed deliverability data for that specific survey. If a survey is throttled, the Survey Deliverability page will show its current status and send rate so you can monitor recovery in real time.
To access the Survey Deliverability page, select Account > Survey Deliverability.
The page displays a data table with one row per live survey and includes the following information:
- Survey name
- Survey launch date
- Survey status
- Bounce rate (last 120 minutes)
- Total bounces / complaints / emails
- Throttle start time
In-product notifications
Agile Research sends in-product notifications to help you stay informed about deliverability issues. Details in the notifications include the following:
Survey throttled notification — When a survey is throttled based on high bounce or complaint rates, Agile Research sends survey owners and account administrators in-product alerts explaining what happened and what actions to take.
Complaint rate warning — When a survey complaint rate exceeds 0.1%, administrators and survey owners receive a warning notification. This is an early alert to investigate and address the issue and not a throttling alert.
Notification frequency — To avoid notification fatigue, Agile Research sends a maximum of one alert per survey per 24-hour period. You will not receive repeated notifications for the same survey within that window.
