Email’s Hidden Halo: How We Proved Email Drives Revenue Far Beyond Its Own Clicks
An online marketplace cut its email frequency and needed to know what email was worth. GA4 only credits email sessions, missing shoppers who read an email then buy later via search, social or direct. OMG’s measurement showed the lift across other channels is nearly four times what GA4 credits to email.
5.7%
Non-email revenue on send days
(Up after 13 of 20 sends)
7.3%
Non-email revenue the day after a send
(Up after 12 of 15 sends)
4x
Revenue lift in other channels compared with GA4’s email credit
Services
- Email Marketing
Industries
- Retail & E-Commerce
Challenges
- GA4 only credits email with sales from email sessions, so its true contribution to revenue was invisible.
- Send frequency had dropped from about 3.6 to 2.2 emails a week year on year, and the client needed to know what that change was costing or saving.
- Without a clear value for email, budget and cadence decisions were based on an incomplete picture.
Strategy & Approach
- Mapped every send day: flagged each send day from email traffic spikes in GA4 across July to October, over two years.
- Compared like with like: measured revenue from every other channel against the same weekday in nearby weeks with no send.
- Used quiet days as a control: tracked the send day and the day after, and compared both against quiet days with no send nearby.
- Turned insight into action: tested a Sunday send on the weakest trading day and aligned paid media budgets to the send calendar.
Key Results
The halo effect (July to October):
- Non email revenue rose 5.7% on send days, up after 13 of 20 sends
- Non email revenue rose 7.3% the day after a send, up after 12 of 15 sends
- Quiet days with no send nearby showed close to 0% change, confirming the pattern
- The revenue lift around each send was close to 4x what GA4 credited to email
What changed as a result:
- A Sunday send lifted non email revenue by 6% compared with the previous four Sundays, bringing the weakest trading day in line with the rest of the week
- Paid media budgets now follow the email send calendar
- A holdout test is planned to confirm the impact
Want to Know What’s Holding Your Email Marketing Back?
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$591K
A boutique real estate agency where mid $20,000s commissions make every listing count. Its database of past vendors, buyers and enquiries only heard from the agency when a listing went live. OMG’s email and SMS reactivation campaign turned those contacts into appraisals and listings, generating $591K in commission over 12 months.
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