Overview
When sending emails to participants, especially at scale, you may encounter rate limiting from Gmail.
Google have recently started enforcing this more seriously and for running events — where communication is often irregular, high-volume and time-sensitive — understanding and avoiding these limits is critical to ensuring participants receive essential information.
What is Gmail Rate Limiting?
Gmail rate limiting is a protective mechanism designed to prevent spam.
If Gmail detects unusual or risky sending behaviour, it will:
Slow down the rate at which your emails are accepted
Temporarily reject messages
In more severe cases, block delivery altogether
Importantly, this is not just about how many emails you send — it’s about how you send them.
Why Running Events Are at Higher Risk
Event organisers often fall into a pattern that Gmail considers high-risk:
Large email lists (thousands of participants)
Long periods of inactivity
Sudden, high-volume sends (e.g. final race instructions)
From Gmail’s perspective, this can resemble spam-like behaviour:
A dormant sender suddenly becoming very active
Recipients who may not strongly recognise the sender
Potentially outdated or unengaged contacts
Key Triggers for Rate Limiting
Understanding what triggers rate limiting is the first step to avoiding it.
1. Sudden Volume Spikes
Sending a large number of emails in a short period is the most common trigger.
Example: Sending 20,000 emails within an hour after weeks of inactivity
Gmail interprets this as abnormal behaviour
2. Inconsistent Sending Behaviour
Long gaps followed by large sends
Irregular patterns across campaigns
Consistency is a key trust signal for Gmail.
How to Avoid Gmail Rate Limits
1. Distribute Sends Over Time
Avoid sending your full list in a single burst.
Best practice:
Break your audience into segments
Send in batches over several hours or days
Example approach:
Time Window | Audience Portion |
Morning | 20% |
Afternoon | 30% |
Evening / Next Day | 50% |
This creates a more natural sending pattern and reduces the likelihood of throttling
2. “Warm Up” Before Critical Sends
If you have not emailed your audience recently:
Send a smaller email campaign first - perhaps to a small group of participants
Follow with your larger, critical communication
This re-establishes trust with Gmail before your main send.
3. Keep Sending Behaviour Consistent
Where possible:
Maintain a regular cadence (even if low volume)
Avoid long inactivity periods
Consistency signals reliability to Gmail.
Recommended Strategy for Race Communications
60 Days Before Event
Begin light communication (training reminders, event info)
Target specific groups of participants (e.g. specific tickets)
Re-engage participants gradually
30 Days Before Event
Send key updates in controlled batches
Again target specific participants but perhaps increase batch sizes slowly (e.g. specific races)
Final Instructions (1–7 Days Before)
Avoid a single large blast if possible
Continue batch sending approach but can be larger
Key Takeaways
Gmail rate limiting is driven by behaviour, not just volume
Sudden spikes in sending are the biggest risk factor
Gradual, consistent sending significantly improves deliverability
Engagement and list quality directly impact your ability to send at scale
Support
If you need guidance on structuring your sends or managing large participant communications, the Let’s Do This team can help you plan an approach that minimises delivery risk.