Proxy Impression vs User Impression

Email advertising environments behave differently from traditional web environments because many email providers route image requests through proxy servers.

Understanding the difference between proxy impressions and user impressions can help advertisers interpret campaign metrics more accurately.

What Is a Proxy Impression?

A Proxy Impression occurs when an email provider’s proxy server requests advertisement images on behalf of the user.

Common proxy environments include:

Apple Mail Privacy Protection
Gmail image proxy
Yahoo Mail proxy
Outlook image proxy

When a user opens an email, the email client may request all images through the provider’s proxy infrastructure before displaying them to the user.

In this case, the ad request originates from the proxy server rather than directly from the user’s device.

What Is a User Impression?

A User Impression occurs when an advertisement is requested directly by the user’s device.

This typically happens when the email client retrieves images directly rather than through a proxy.

User impressions generally provide more accurate signals regarding:

Device type
Geographic location
Engagement context

However, in modern email environments, a large portion of traffic originates from proxy environments.

Why Proxy Impressions Exist

Email providers use proxy servers primarily for:

User privacy
Security
Malware scanning
Image caching

Proxy servers help prevent advertisers and senders from directly accessing user device information.

How Proxy Impressions Affect Reporting

Proxy traffic can influence several reporting metrics.

Impression Counts

Some email clients preload images when an email is opened. This can result in impressions being recorded even if the user does not actively view every element of the email.

Because of this, impressions should be interpreted as potential exposure rather than guaranteed visual engagement.

Geographic Accuracy

Proxy servers may mask the user’s exact location.

Typically:

Country-level location is reliable
State or city-level location may be less accurate

Advertisers targeting proxy traffic should generally rely on country-level targeting.

Device Identification

Proxy servers may request images using device signals that differ from the user’s actual device.

For example:

A mobile email client may request images through a proxy that appears as a desktop environment.

To help advertisers analyze traffic environments, reporting includes a Device / Proxy dimension that identifies proxy environments separately from direct device traffic.

Best Practices When Evaluating Proxy Traffic

When reviewing campaign performance:

Focus on engagement metrics such as clicks and conversions
Compare performance across device and proxy segments
Use country-level geo targeting when targeting proxy environments

Proxy impressions are a normal part of email advertising and should be expected when running campaigns across large email audiences.