CaptainVerify verified over 126 million email addresses in 2025. Only 57% were valid. On a list of 100,000 contacts, 43,000 can’t receive any message, yet most companies send them campaigns every month, paying their emailing platform for each send. We know the purchase price of an email address. Its true net value, much less.
Why email ROI is the highest among all channels
Email marketing generates an average of 36 to 45 euros for every euro invested according to the Efficy 2025 study, based on the analysis of 3.2 billion emails sent by its clients in 2024. It is the marketing channel with the best return on investment that is measurable, ahead of social media and SEA.
This figure varies by sector. Retail and e-commerce achieve 45€ return per euro spent. Marketing agencies are around 42€. Software publishers generate 36€. 52% of consumers made a purchase directly from a marketing email in 2024 (Efficy 2025), compared to 39% from a social media post.
Email remains the only channel where the brand directly addresses someone who has consented, without intermediary algorithms, without ad auctions. It’s a direct line to a potential buyer. But this line is only valuable if it works.
What an active email subscriber is really worth
The value of an email subscriber is measured by the Revenue Per Subscriber: the revenue generated per active contact over a given period. For an e-commerce, the average is around $6.86 per subscriber per year according to data compiled by Omnisend on online stores.
This number conceals significant gaps. An e-commerce with a list of 19,000 active subscribers and a well-configured automation program can generate $50,000 per month, or $2.63 per subscriber each month. Automated emails (welcome sequences, abandoned carts, post-purchase follow-ups) significantly outperform traditional newsletters in engagement. Brevo’s 2025 benchmark, based on the analysis of 44 billion emails, measures an average open rate of 31.22% and a click rate of 3.64% across all types.
The distinction between active subscriber and dormant contact is decisive. A contact who hasn’t opened an email for 12 months degrades the sender’s reputation without generating any revenue. Its value is negative.
Purchase price is not the value
You can buy an email address for between €0.10 and €0.35 in B2B according to prospect files available on the French market. Rent ranges between €0.12 and €0.75 per contact. These prices give the illusion of a good deal: a qualified contact for less than one euro.
Two realities are missing from this calculation. A purchased address is not opt-in: the person has not consented to receive your communications, which generates high complaint rates and exposes the sender to immediate deliverability penalties. Additionally, 32% of brands do not communicate a clear privacy policy during collection, which weakens the legal basis for sending under GDPR (dotdigital, Hitting the Mark).
The real value of an email address comes down to 3 factors: the technical validity of the address, the explicit consent of the owner, and their level of engagement over time. The purchase price does not provide any information on any of the three.
The Silent Degradation: 23% Loss per Year
This is where the difference between a revenue-generating list and a costly list becomes evident. Of the 126 million addresses verified by CaptainVerify in 2025, 43% were not usable as is: 8.2% were outright invalid (non-existent domain, deleted mailbox), 8.8% were risky addresses, 4% were role addresses (contact@, info@), 2.5% were catch-all, and 0.2% were disposable addresses.
The causes vary: change of employer (a professional address disappears with the job), abandonment of a personal mailbox, domain closure, typos at signup. Invalid and risky addresses alone represent more than 21 million contacts out of the 126 million verified. The 3.2 million catch-all addresses identified add a layer of uncertainty: they seem valid but generate unpredictable bounces.
In practical terms: on a list of 10,000 contacts collected 18 months ago without regular verification, it is estimated that 3,000 to 3,500 addresses are now problematic. If the emailing platform charges €0.002 per email sent, these useless sends represent €6 to €7 wasted per campaign, even before considering the impact on the sender’s reputation which degrades the deliverability of the entire list.
When the bounce rate exceeds 2%, the entire list suffers
Email deliverability works like a credit score: each hard bounce, each spam complaint degrades the sender’s reputation with access providers (Gmail, Outlook, Orange). A bounce rate above 2% is the threshold at which ESPs (Email Service Providers) begin to reduce inbox placement rates.
The cost of poor deliverability is rarely measured directly, but it is real. If 20% of campaign emails end up in spam instead of the main inbox, 20% of potential ROI disappears. On a base of 50,000 contacts with an average ROI of €36/€ invested, the difference between 95% deliverability and 80% can represent several thousand euros in revenue per campaign.
“Out of 126 million addresses submitted to our verification system, only 57% were confirmed as valid. The remainder are divided among invalid, risky, catch-all, and disposable addresses.” (CaptainVerify, 2025)
How to calculate the net value of your list
Let’s take a list of 20,000 contacts with 57% valid addresses (rate observed by CaptainVerify on 126 million verifications in 2025), an open rate of 25%, a click rate of 3%, an average cart of €80, and an email-to-purchase conversion rate of 2%.
| Indicator | Unverified list (100%) | Verified list (57% valid) |
|---|---|---|
| Contacts sent | 20,000 | 11,400 |
| Emails opened (25%) | 5,000 | 2,850 |
| Clicks (3%) | 600 | 342 |
| Estimated purchases (2% of clicks) | 12 | 7 |
| Generated revenue (cart €80) | €960 | €560 |
| Estimated bounce rate | >5% (penalizing) | <2% (healthy) |
| Impact on sender’s reputation | Gradually degraded | Preserved |
Sending to the entire list generates more revenue in the short term on paper but degrades the sender’s reputation, reducing main inbox placement for all subsequent campaigns. Over a year, a healthy list of 11,400 contacts generates more than an unverified list of 20,000 if deliverability collapses in the meantime.
Verifying your list: protecting ROI, not a technical expense
If every euro invested in email marketing returns 36 to 45 euros but 43% of a list’s contacts cannot receive the campaigns, the real ROI is almost halved mechanically. Email address verification is not an additional cost: it is what allows the promised ROI to be realized concretely.
Verifying a list before the first send eliminates invalid addresses, catch-all addresses, and spam traps from registration. Re-validating every 3 to 6 months follows the natural degradation pace (23% per year, about 2% per month). Removing inactive contacts for over 12 months preserves the open rates and sender’s reputation.
An email address is worth what it generates, not what it cost to collect. The one that bounces with every send is not neutral in the list: it lowers the performance of all the others.
What is a valid email address?
A valid email address is one with correct formatting, an existing domain, and an active inbox capable of receiving messages. An email verification distinguishes valid addresses, invalid addresses (non-existent domain, deleted inbox), catch-all addresses (domain configured to accept all emails without delivery guarantee), and risky addresses (spam traps, disposable addresses).
How much does it cost to verify an email list?
The cost of email address verification is typically between €0.001 and €0.005 per address for large volumes. For a list of 10,000 contacts, the verification cost is therefore between €10 and €50, compared to the hundreds of euros in potential value that a healthy list can represent in a well-targeted email campaign.
How frequently should an email list be verified?
A quarterly verification is the minimum, monthly for rapidly growing lists. An unverified list for 6 months may have lost over 10% of its active addresses without the campaign statistics clearly indicating it.
