In some reports, you may see an email open rate above 100%. At first glance, this looks impossible – how can more emails be opened than were delivered?
This is usually not caused by a calculation error, but by how the metric is defined or how the date range is applied.
Counting all opens instead of unique opens
Because the same person can open the same email multiple times, counting every open event would quickly inflate the number of opens and make the open rate misleading.
To avoid this, use unique opens:
Unique opens = each customer is counted once per email, even if they open it multiple times.
For example, if one customer opens the same email three times, that counts as 1 unique open, but 3 total opens.
The standard unique open rate calculation is:
Open rate = (Number of unique recipients who opened the email ÷ Number of delivered emails) × 100You can use either "First" or "Last" – both options will count the customer only once.
Date range mismatch
Another possible reason the open rate appears higher than 100% is a mismatch between when emails were delivered and the date range used in the report.
Every time a customer opens an email, a new open event is logged for that email in the customer’s profile. The delivered email is recorded once, when the campaign is delivered. Each subsequent opening of that same email creates a new open event — even days or weeks later.
Let's take a look at this example (imagine you are building a report in December):
- The campaign was delivered months ago in July.
- Many customers received the email back in July.
- Those customers can still open the same email today, next week, or any time in the future, as long as they keep it in their inbox.
If you set the report’s date range to "Last 30 days", the system:
- Counts all open events that happened in the last 30 days (even if the original email was delivered months earlier).
- Counts only the delivered emails that happened in the last 30 days in the denominator.
If the campaign sent few or no emails in the last 30 days but people are still opening old emails, the open rate can exceed 100%.
How to confirm that the date range is the cause
- Identify when the campaign started
Check the campaign’s start date and the time when most deliveries occurred. If this is much earlier than your current report range, it's a strong hint. - Change the report date range
Switch from a short window (for example, "Last 7 days" or "Last 30 days") to a broader range, such as "Last 3–6 months" or "Lifetime". With the wider range, you should see that the total delivered and unique opens now align more realistically.
How to count opens that happened on the same day the campaign was sent?
First, we need to understand the difference between these two attributes stored in the campaign event:
sent_timestamp– when the email was sent from Bloomreach (send time).timestamp– when a specific event (open, click, etc.) occurred.
To make the date range reflect only opens that belong to emails sent in that same period, we need to add a filter in your report:
- In the report filter, add a condition with
sent_timestamp. - Set the
sent_timestamprange to match the overall report date range (for example, "Today", "October 1–31", etc.).
Once you do this, only campaign events with a sent_timestamp in the selected window are included. Opens (and clicks) from emails sent outside that window are excluded.
Events expiration
A less common reason might also be the expiration of events. In this case, the expiration of the delivered event. If a campaign event with status 'delivered' has expired, it's effectively deleted from the database and no longer exists. As reports, metrics, and all other campaign analytics are based on campaign events, this will also affect the resulting numbers. If campaign events with status 'delivered' have expired and the events originating from the same campaign with status 'opened' are still in the database, this could contribute to the discrepancy.