Email marketing, by the numbers
The state of email marketing, measured from real campaigns
Inbox Archive detects the email service provider, tracking and personalization tech, and campaign type behind every email it stores. Across 154 brands and 4,253 real campaigns, here is what the stack and tactics actually look like, measured from live sends and updated as new mail lands (current as of September 11, 2026).
Which email service providers brands actually use
Klaviyo is the most-used ESP among archived brands: 66 of 154 (43%) send with it. A brand can appear under more than one provider when it sends from several.
Share of campaigns by ESP
- Klaviyo 43%
- Salesforce Marketing Cloud 22%
- Mailgun 8%
- Braze 7%
- SendGrid 7%
- Iterable 5%
- Other 8%
Brands using each provider
Which domain the mail actually comes from
Deliverability guides tell brands to send marketing from a dedicated subdomain rather than their root domain. In practice, 46% of brands do. The most popular label is email. (as in email.brand.com), chosen by 20% of subdomain senders. Measured across 154 brands with a known website; a brand can appear under more than one style when it sends from several domains.
What the From address sits on
- A subdomain of their site (email.brand.com)
- 71 brands · 46%
- The website domain itself (brand.com)
- 72 brands · 47%
- A separate domain entirely (brand-email.com)
- 15 brands · 10%
Most common subdomain labels
Tracking & personalization tech
Beyond the sending ESP, Nifty Images is the most common add-on layer, found in emails from 5 brands.
What brands actually send
The most common campaign type is Promotions & Sales (45% of all campaigns).
Tactics & techniques
6% of campaigns carry a promo code (239 campaigns from 52 brands). How often each rendering technique shows up:
- Dynamic / open-time content
-
2%
- A dark-mode variant
-
10%
- Animated GIFs
-
26%
- A promo code
-
6%
How brands handle unsubscribes
98% of campaigns carry a List-Unsubscribe header,
the one that lets Gmail, Apple Mail and Yahoo show an unsubscribe button next to the sender's name;
2% (64 campaigns) go out without one.
97% support one-click unsubscribe (RFC 8058, an https link plus a
List-Unsubscribe-Post header), which Gmail and Yahoo have required of bulk senders since 2024.
7 brands (5%) never include it in any campaign.
- Carry List-Unsubscribe
-
98%
- Support one-click unsubscribe
-
97%
- No unsubscribe header at all
-
2%
- Brands that always include it
-
88%
Of the campaigns that carry the header, 69% offer both a link and a mailto address, 31% a link only, and 0% a mailto address only.
When brands hit send
Thu is the busiest day (16% of campaigns) and Sat the quietest (11%). The single most common hour to send is 9am. Times are US Eastern. Counts 4,012 scheduled campaigns: welcome, cart and order emails are left out here, because they go out when a subscriber acts rather than when the brand chooses to send.
Day of week
Hour of day (US Eastern)
How often brands send
The typical brand sends 3.5 campaigns a week, measured across 131 brands with a long enough run of mail to judge.
What subject lines look like
The median subject runs 33 characters across 6 words, and 19% carry at least one emoji.
- Median length
- 33 chars
- Median words
- 6
- 40 chars or under
- 71%
- With an emoji
- 19%
How much is actually in an email
The median campaign carries 184 words of copy and 11 images, measured across 4,253 campaigns.
- Median words of copy
- 184
- Median images
- 11
How this is measured
Every figure comes from real emails captured in Inbox Archive, not surveys. The ESP is detected from message headers and sending infrastructure; tracking and personalization tech from asset and click domains in the HTML; campaign type and promo codes from the email content itself. Sending domains come from the From address of each campaign, compared against the brand's own website. Unsubscribe figures read the List-Unsubscribe and List-Unsubscribe-Post headers of each message as it arrived. Figures cover 4,253 published campaigns from 154 brands sent between Nov 2019 and Sep 2026, and refresh as new mail is archived. Browse the underlying data by provider, tracking tech, or campaign type.