Where our numbers come from
Every claim, benchmark, or technical specification cited across outsolvi.com traces to a source. This page consolidates the external publications, internet standards, and Outsolvi internal data we cite, so you can check the work.
Not using Outsolvi yet? Every number on this site traces to something you can check. The product applies the same standard to your own sends: each open graded on how likely it was a real person. Start free
The taxonomy below covers Apple MPP documentation, the 2024 bulk-sender authentication rules from Google, Yahoo, and Microsoft, the IETF RFCs defining SPF/DKIM/DMARC/BIMI/one-click unsubscribe, the major enterprise email-scanner vendors' public documentation, the canonical B2B engagement studies, and Outsolvi's own production-data claims with sample sizes.
Apple Mail Privacy Protection (MPP)
Apple Mail Privacy Protection loads remote images for everyone who switches it on, so an Apple Mail open often isn't a read. The sources below document how it works and how much email it touches.
With Protect Mail Activity on, Mail downloads remote content in the background by default, whether or not you engage with the email, through two relays run by different companies.
Apple Mail accounted for 62.26% of the opens Litmus measured in July 2026, across more than a billion opens from all the senders it tracks. Litmus publishes no industry or B2B split.
How MPP works: Apple routes email through proxy servers that pre-load images, including tracking pixels, whether or not the reader opens the message.
Initial MPP launch with iOS 15.
Bulk Sender Authentication Rules (Google + Yahoo + Microsoft)
The February 2024 bulk-sender rules from Google and Yahoo reshaped deliverability requirements for any sender above 5,000 messages/day to consumer addresses.
Authentication for every sender, and for senders of more than 5,000 messages a day to Gmail accounts, one-click unsubscribe and the spam-rate rule: keep it below 0.10% in Postmaster Tools and never reach 0.30%.
The October 2023 announcement of the bulk-sender rules that took effect in February 2024.
Yahoo's published expectations for high-volume senders, aligned with Google's bulk-sender rules.
Microsoft's matching bulk-sender rules for Outlook.com, Hotmail, Live.com.
SPF / DKIM / DMARC / BIMI Standards
The internet standards that define email authentication. RFC numbers below are the canonical sources.
Canonical SPF specification including the 10-DNS-lookup limit and qualifier syntax.
DKIM signature standard including selector syntax and signing algorithm specifications.
Canonical DMARC specification including the three policy modes (none, quarantine, reject) and alignment rules.
BIMI experimental specification covering selector format, SVG Tiny PS format requirements, and VMC linkage.
One-click unsubscribe header standard required by Google and Yahoo bulk-sender rules.
Corporate Email Scanners (Defender / Mimecast / Proofpoint)
The three dominant enterprise email security gateways. Each pre-fetches links and images for malware scanning, contaminating click and open tracking.
Microsoft documents Safe Links pre-fetching behaviour; basis for filtering scanner clicks on Microsoft 365 tenants.
Documents Defender's attachment-fetch behaviour which contributes to pre-fetch opens.
Mimecast rewrites the links in inbound email and scans each destination, so a tracked link can be fetched by Mimecast's systems as well as by the person.
Proofpoint rewrites the links in inbound email and sandboxes them, so a tracked link can be fetched by Proofpoint's systems as well as by the person.
Billions of opens and clicks classified in real time, reported by recipient type. At large corporate inboxes behind security gateways, 80-95% of clicks were bots; on Outlook.com and Hotmail about 30%; and about half of consumer email opens have been non-human every year since 2023. Omnivery sells bot detection, so this is a vendor's study.
B2B Engagement & Lead-Response Studies
The benchmark studies for follow-up timing, response rate, and pipeline conversion that Outsolvi cites in its content.
Six companies, 15,000+ web leads and 100,000+ call attempts: the odds of qualifying a lead dropped 21 times when the company called at 30 minutes instead of 5.
A survey of 632 B2B buyers (August to September 2024) found buying groups ranging from five to 16 people across as many as four functions. Gartner's older six-to-ten figure is no longer on its site.
1.25 million leads at 42 US companies: firms that tried to reach a lead within an hour were nearly seven times as likely to qualify it as firms that waited even an hour longer. An audit of 2,241 companies found 37% responded within an hour and 23% never did.
Outsolvi Internal Data
Numbers read directly from Outsolvi's tracking engine: how opens are graded and how accuracy gets checked. We don't publish statistics about customers' email.
Internally each grade maps to a score: verified 100, most likely human 70, possibly human 20, machine 0. The counting floor is 25, so verified and most likely human opens count and the other two do not. Customers see the grade and its reason, never the number. These are configuration values read from the tracking engine, not estimates.
There is no single accuracy figure, and we would rather say so than invent one. What runs is a weekly precision report: for every classification rule, how often a user confirmed it against how often a user overrode it, over a rolling 30 days. A rule with too little feedback reports nothing rather than a guess.
How we cite, when we update, and what we won't claim
Citation policy. Every quantitative claim on outsolvi.com that comes from outside Outsolvi's own data is attributed to a publisher with a live link. If we can't cite the source, we don't publish the number.
Update cadence. Each long-form content page carries a lastUpdated date that reflects the most recent substantive review. We bump this only on real revisions, not on auto-rebuilds.
What we won't claim. We don't fabricate testimonials, invent customer counts, or cite paid research as independent. We don't publish statistics drawn from customers' email. Where a number comes from Outsolvi itself, it is a setting read from the product, and we say so.
Methodology. The methodology page documents how we grade opens, where benchmarks come from, and how the test environment works.
You checked our sources. Now check our numbers on your own inbox.
Every accuracy claim on this page is testable with the 14-day free trial. Graded opens from your first tracked send. No credit card.
Nate built Outsolvi after watching every email-tracking tool he had ever used lie to him about opens. Outsolvi grades every open as a person or a machine, in Outlook and Gmail, so the number on the dashboard is one a rep can actually act on.
We update these pages when the underlying mechanics change. new mailbox-provider rules, new tracker behavior, new measurement gaps. The dates above are real revisions, not auto-touches.