Thread by @WolfieChristl

"We partner with more than 70 providers of mailbox and security solutions, covering 2.5 billion inboxes ... Also feeding into this data platform is our consumer network of more than 2 million consumers"

Return Path, email data harvesting since 1999:
returnpath.com/about/

In 2017, Return Path acquired ThreatWave, an 'email data company that captures and processes billions of emails each month and parses these messages into a unique data source for email intelligence', for 'Reputation, Security, and Marketing Intelligence': returnpath.com/newsroom/retur…

'we built a big data machine that parses 1 terabyte+ data a day, taking 200 million messages daily sent to 90 million+ email addresses and breaking it into structured data components'

'we receive email organically from 196 countries daily'

threatwave.com/about-us/

Return Path doesn not only gather data from email inboxes via partner apps, but also runs apps itself, e.g. Shopami, Unsubscriber, Organizer, Whisker, Notifier (returnpath.com/return-path-co…).

One of them, getunsubscriber.com, claims to have 'over 6 million users'.

Another app by Return Path, getorganizer.com, claims to have 'over 1 million users'.

Return Path provides an 'email API'. Third-party developers can use it to access and handle Gmail, Outlook or any IMAP mailboxes.

They advertise their service as 'free to use for most cases'.

However, this includes 'anonymous and aggregated data sharing'
context.io/pricing/

Where Return Path doesn't have direct access to email inboxes, it seems to use other tech to track the behavior of email recipients anyway.

In @s_englehardt et al's paper on email tracking returnpath.net is amongst the top 10 third-party domains:
freedom-to-tinker.com/2017/09/28/i-n…