Email deliverability: the performance lever that marketing teams too often neglect

Email remains, on paper, the marketing channel with the highest ROI, generating between $36 and $42 for every dollar invested, according to data from the Data & Marketing Association. But this figure relies on an assumption that many teams take for granted: that their emails actually reach their recipients' inboxes. This isn't always the case. According to Validity's Email Deliverability Benchmark 2025, one in six legitimate marketing emails never reaches the inbox. Globally, the average inbox placement rate is around 83% to 84%. In concrete terms, for a company that sends 100,000 emails per month, this represents between 15,000 and 17,000 messages that disappear before even being seen—messages that have been designed, segmented, tested, and for which the sending cost has been duly billed. Deliverability: The Blind Spot of Dashboards. The problem lies partly in how sending platforms present the data. The vast majority of tools display a "delivery rate" that counts all emails accepted by the recipient's server, including those that land directly in the spam folder. This figure is almost always above 98%, which reassures marketing teams. But it says nothing about what email filters do with these emails afterward.

Actual deliverability, the effective inbox placement rate, is a much more difficult metric to measure and is rarely highlighted by platforms. Yet it's what determines the open rate, and therefore the entire performance chain that follows: clicks, conversions, and attributed revenue.

What Email Algorithms Really Evaluate

Gmail, Outlook, and other major email providers have significantly refined their filters in recent years. They no longer evaluate just email content or spam trigger keywords.

Their algorithms now analyze a set of behavioral and technical signals: Sender reputation: built from the domain's sending history and the IP addresses used. A poorly cleaned database, with high bounce rates or frequent spam reports, cumulatively degrades this reputation. Technical authentication: since early 2024, Gmail and Yahoo have required all high-volume senders to configure SPF, DKIM, and DMARC. Microsoft is expected to follow suit soon. These protocols serve to prove that emails sent on behalf of a domain are legitimate; their absence or incorrect configuration is now a direct filtering criterion. Recipient engagement: open rates, click-through rates, reply rates, but also negative behaviors such as unread deletion and spam flagging, feed in real time into the trust score assigned to each sender. This explains why lists that are too large and not segmented enough can paradoxically degrade deliverability even when the content is relevant. Validity's data also shows a significant difference between regions: Europe has an inbox placement rate of 89.1%, significantly higher than the global average. An advantage that specialists largely attribute to the requirements of the GDPR, which have pushed European senders towards stricter opt-in practices and better-qualified contact databases.

Open Rates Under Double Pressure

In France, the average email campaign open rate is 18.22% according to DMA France data for 2025. This already modest figure could soon become even less reliable as a performance indicator.

On the one hand, email clients' privacy protections (Apple Mail Privacy Protection in particular) artificially inflate measured open rates. On the other hand, the CNIL (French Data Protection Authority) launched a public consultation in June 2025 on a draft recommendation that could require explicit consent before any use of tracking pixels in emails, classifying these trackers as cookies subject to the rules of the ePrivacy Directive. If this recommendation comes into effect, open tracking would no longer be automatic for contacts who have not explicitly consented, rendering this metric largely unusable for some databases.

What deliverability reveals about the quality of an email strategy

Deliverability is not just a technical issue. It directly reflects the quality of sending practices as a whole.

A database collected via clear opt-in mechanisms generates fewer spam complaints.

Segmented mailings produce better engagement signals. Regularly cleaning inactive contacts reduces bounce rates. DMA data indicates that senders with a double opt-in policy have inbox placement rates that are 10 points higher than those without. In other words: good database management practices, list hygiene, and relevant content are not only useful for engagement, they directly determine the ability of emails to reach their recipients. This is why choosing an email marketing software that natively supports SPF/DKIM/DMARC authentication, automatic hard bounce removal, and sender reputation monitoring is not a technical detail, but a key performance criterion.

Rethinking Campaign Management

Faced with these developments, several practices deserve to be systematized:

Regularly audit actual deliverability, not just the delivery rate displayed by the platform. Tools like Google Postmaster Tools (free) or specialized monitoring solutions allow you to visualize your domain's reputation and its effective placement rate with Gmail. Monitor your spam complaint rate to stay below the critical threshold of 0.1%. Above this level, the risk of mass filtering by major email providers increases significantly. Switch to clicks and conversions as your primary metrics, anticipating the potential restriction of open tracking. These are more reliable indicators, less susceptible to technical distortions, and less likely to be affected by regulatory changes. Segment and remove inactive contacts: those who haven't opened or clicked on any emails in 6 to 12 months represent a dead weight for your sender reputation. Integrating them into re-engagement sequences, then removing them if no response is observed, is one of the most effective actions for stabilizing deliverability. Deliverability is not a topic reserved for technical teams. It is a marketing discipline in its own right, at the intersection of data management, sending practices, and infrastructure selection. In 2026, in a context where email algorithms are more demanding and regulations stricter, making it a top-tier KPI is no longer optional.