# Re identification risk emails carry with pseudonyms > Re identification risk emails carry: consistent pseudonyms keep links across messages. What Troveo, the ICO and the Spirit union say, and what to ask a buyer. By Matt Burns, Vaultfish. Canonical: https://vaultfish.com/answers/re-identification-risk-emails Published: 2026-10-07 Updated: 2026-10-14 ## The short answer Emails carry re-identification risk because consistent pseudonyms keep one person's messages linked across your archive. Troveo shows labels like PERSON-014. Someone with clues like job titles or rare incidents could rebuild identities. A lawyer should review your archive. Names are the easy part of an email. The links between messages are the harder part, and buyers want to keep them. ## Why do consistent pseudonyms keep links? A pseudonym that changes from one message to the next would break the thread. So the swap is consistent, and the same label keeps one person's work connected across records. [Troveo's business data page](https://www.troveo.ai/business-data) shows a before and after in which PERSON-014 and EMAIL-019 stand in for a customer and an address. David Revland, who works on human data at micro1, said in an undated recorded forum talk that micro1 swaps a name for a consistent stand-in across tools, so the cross-tool trail survives. ## What do emails add that other records do not? An email thread carries a sender, recipients, replies and dates. [Troveo](/buyers/troveo) describes what a buyer receives from email as threads with senders, recipients and linked responses. Those fields are the links. My reading is that the same fields can point back to a person when a job title, a rare incident or a signature block stays in the text. The [UK ICO](https://ico.org.uk/for-organisations/uk-gdpr-guidance-and-resources/data-sharing/anonymisation/pseudonymisation/) makes the same point about context: people can stay indirectly identifiable through additional information or other techniques, even when no key is held. ## What did the Spirit union object to? [Time](https://time.com/article/2026/08/25/google-spirit-airlines-ai-data-RL/) reported that the flight attendants' [union objected](https://storage.courtlistener.com/recap/gov.uscourts.nysb.331039/gov.uscourts.nysb.331039.1489.0.pdf) because the dataset keeps referential integrity, so even anonymized information about members could be reconstructed. The court's privacy ombudsman [wrote](https://storage.courtlistener.com/recap/gov.uscourts.nysb.331039/gov.uscourts.nysb.331039.1684.0.pdf) on 5 Oct 2026 that she did not examine risks to employees or third parties. My [Spirit Airlines page](/answers/spirit-airlines-data-sale) has the timeline, and the [de-identification page](/answers/data-de-identification) compares the legal tests. ## What do the legal tests say about pseudonyms? The [UK Information Commissioner's Office](https://ico.org.uk/for-organisations/uk-gdpr-guidance-and-resources/data-sharing/anonymisation/pseudonymisation/) says pseudonymised data stays personal data for anyone who holds the additional information. The [Justice Department's bulk-data rule](https://www.law.cornell.edu/cfr/text/28/202.206) counts data whether or not it is pseudonymized, as the [DOJ rule page](/answers/does-the-doj-bulk-data-rule-apply-to-selling-company-data) explains. Recent studies on whether language models can match accounts and find missed identifiers are on my [re-identification study page](/answers/can-ai-re-identify-anonymized-emails-and-slack-messages). ## What should an owner ask the buyer? 1. Who holds the key that maps labels back to names? 2. Do links between messages and across tools survive, and why? 3. Does anyone test for re-identification after the swap? 4. Are employees in the archive, and what did they agree to? My [rights check](/rights-check) lists what to settle with counsel, and the [risk map](/risks) lists what published buyer terms say. Talk to a privacy or commercial lawyer in your state before you sign. Figure: steps Name swapped for a label -> Same label, thread order intact -> Context can point to a person. A consistent label keeps the links between emails, and links plus context are where re-identification starts. micro1 may pay us a referral fee if a company we introduce goes ahead with it. [How we are paid](https://vaultfish.com/disclosure) _Vaultfish helps you run the process. We are not lawyers and this is not legal advice. If you need counsel who knows this area, we can point you to one._ ## Sources - [Troveo's business data page](https://www.troveo.ai/business-data) - [UK ICO](https://ico.org.uk/for-organisations/uk-gdpr-guidance-and-resources/data-sharing/anonymisation/pseudonymisation/) - [Time](https://time.com/article/2026/08/25/google-spirit-airlines-ai-data-RL/) - [union objected](https://storage.courtlistener.com/recap/gov.uscourts.nysb.331039/gov.uscourts.nysb.331039.1489.0.pdf) - [wrote](https://storage.courtlistener.com/recap/gov.uscourts.nysb.331039/gov.uscourts.nysb.331039.1684.0.pdf) - [Justice Department's bulk-data rule](https://www.law.cornell.edu/cfr/text/28/202.206)