D-Mail#
| Full name | De Lorean Mail |
| Coined by | Rintaro Okabe |
| Medium | SMS text message |
| Transmitter | Phone Microwave |
| Payload limit | 36 bytes per burst (12–18 characters Japanese) |
| Direction | Present → past only |
| Observable effect | Worldline shift at moment of receipt |
| Detection | SERN monitoring network |
| Countermeasure | Sending a cancelling D-Mail ("undo mail") |
| Total confirmed sends | 11 (this attractor field) |
| Status | Retired practice |
A D-Mail (De Lorean Mail — Okabe does not apologize for the name) is a text message transmitted into the past via the Phone Microwave. It is the lab's founding discovery, the trigger for every worldline shift in the lab's recorded history, and the reason this wiki's event pages must all be annotated with divergence values. As lab doctrine now states, in letters large enough to read from the doorway: a D-Mail cannot be unsent, only outbid.
A D-Mail arrives on a real handset in the past as an ordinary message — no glow, no fanfare, sender field garbled. The recipient acts on it (or doesn't), causality re-knits around the new information, and the worldline shifts to accommodate the changed history. From inside the new worldline, the message has "always" been received; only observers with Reading Steiner recall the version of events it overwrote.
Payload capacity is the binding constraint. The PhoneWave's aperture stays open for microseconds, enough for roughly 36 bytes per burst. Longer messages fragment into multiple bursts that can arrive out of order, minutes apart — the lab's second D-Mail arrived as three fragments across two hours, and the recipient read them in exactly the wrong order.1
Anatomy of a send
- Compose SMS on docked handset
- Set target time offset
- Microwave runs (do not open)
- Message ceases to exist here
- World quietly rewrites itself
The lab's accumulated, expensively-learned guidance:
| Rule | Reason | Learned in |
|---|---|---|
| Never send about money | Divergence explodes; SERN flags gambling anomalies | Episode 05 |
| Never send about people's lives | The attractor field routes around it, cruelly | Episode 12 |
| Shorter is safer | Fragmentation scrambles meaning | Episode 03 |
| Photograph the meter first | Only way to measure what you did | Episode 06 |
| The undo mail must contradict, not delete | The past cannot un-know; it can only be re-persuaded | Episode 13 |
An "undo mail" does not restore the original worldline — it moves to a third worldline that closely resembles the first. The Divergence Meter readings before and after an undo never match exactly. The difference has never been observed to be zero.
A one-line test message. It arrived one week in the past, and the shift it caused was large enough that the lab's founding membership changed — the canonical example of how disproportionate the effect can be. Covered in Episode 01 and Episode 02.
A lottery-number mail sent on behalf of a friend. The numbers arrived garbled, the winnings never materialized, and the divergence cost took three undo mails to claw back. See Episode 10.
The final D-Mail sent from the lab was an undo mail — the one that pulled the worldline out of the Alpha attractor field entirely. Its 12 characters are redacted on this wiki by unanimous lab vote. Episode 13.
Okabe named it after the time-travelling car from a film he claims to have watched "for research." Attempts to rename it ("Retro-SMS," "chronomail," Daru's unprintable suggestion) all failed to stick. The abbreviations table on this wiki lists D-Mail as canonical, so the argument is officially over.
Every D-Mail transits the public cellular network for the mundane half of its journey, which is how SERN's monitoring net caught the lab so quickly — the temporal burst is exotic, but the SMS itself is just an SMS. Later sends were routed through a chain of anonymizing relays Daru assembled, which bought weeks at most. The uncomfortable lesson, recorded in the handbook: information that changes the past is still information, and information leaks. For the theoretical framing of why worldlines converge despite interference, see Attractor field theory and the overview at Many-worlds interpretation.
Footnotes#
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The resulting misunderstanding is commemorated by a small dent in the lab's refrigerator door. ↩