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Mk-I · Build 001

We're building a rocket that flies its own mail server.

At one million emails warmed, it launches. On the way up, a mail server bolted into the airframe opens an SMTP connection, signs a message with its own DKIM key, and delivers it, from the air, over radio, with no relay on the ground.

Emails warmed at launch
Things in one flight
Bays
What's actually been done before

Email from a vehicle is old. A server in the air is not.

Astronauts have sent email since 1991, Shannon Lucid and James Adamson, from Atlantis on STS-43. The ISS has had email for decades. Sending a message from a vehicle is not new, and we aren't going to pretend otherwise.

But every one of those messages was sent by a client talking to a mail server on the ground. The server has always stayed on Earth. Shuttle, station, weather balloon, aircraft, all of them relayed.

Nobody has flown the server itself. That's the part we're going after.

The difference is easier to see as a picture. On the left, vehicles that all talk to a server on the ground. On the right, a rocket that carries the server with it.

STS-43, Atlantis. Shannon Lucid and James Adamson.

Left: a client in the air, a server on the ground. Right: the server in the air.

Four things, one flight

What the flight is for.

Four firsts, all from the same server. Each one is quoted from the project, with a plain-words note on what it means.

Thing 1 of 4

An SMTP session opened from the air

The Pi holds the connection itself. The ground station is a radio modem, not a relay. It forwards packets and nothing else.

In plain words

SMTP is the language mail servers use to hand a message to each other. A session is one conversation: a server connects, says who it is, names the sender and the recipient, and passes the message across.

Normally that conversation happens between two servers on the ground. Here the Pi, inside the rocket, is the one holding it, and the radio is only the wire it travels over.

Related
Thing 2 of 4

An inbox-placement test in flight

An inbox placement test, sent to a few test inboxes. We find out whether a rocket lands in the primary tab.

In plain words

Inbox placement is the question of which folder a message lands in: the primary inbox, another tab, or spam. A seed mailbox is a mailbox set up only to receive test messages, so you can look and see where they went.

The product's own placement test works the same way, from the customer's mailbox. Until Warmerly has dedicated test inboxes at Gmail and Outlook, it goes to Warmerly-run warmup mailboxes and is a guide.

Related
Thing 3 of 4

A DMARC report from a flying domain

Comes free once the first one works, and is very funny if you know what DMARC is.

In plain words

DMARC is a record in a domain's DNS that tells receiving mail servers what to do with mail that fails its checks, and asks them to send reports back. The report is the summary a receiving provider sends about the mail it saw from that domain.

If the first message gets through, a report about a domain that was in the air comes with it.

Related
Thing 4 of 4

Authoritative DNS served from a rocket

The flight domain answers its own queries for the duration of the flight.

In plain words

DNS is the lookup system that turns a domain name into the records that say where its mail goes and which servers may send for it. An authoritative server is the one that holds the official answers for a domain.

For the length of the flight, the rocket is that server for the flight domain.

Related

The path of a message: the Pi inside the rocket holds the SMTP connection, the radio carries it, and the ground station passes packets along. No relay on the ground. Mailboxes at the other end are the seed mailboxes of the placement test.

As far as we can establish, none of these has been done before. We can't prove a negative, so if you know otherwise, tell us and we'll say so on this page. You can get in touch here.

Nose to tail

Five bays, and what each one is for.

The airframe from the tip to the motor mount. The first line of each is the project's own description. The second line says what the words mean.

  1. Nosecone

    GPS tracker on its own battery, chirping position once a second. It has to keep working if everything else stops, because this is how we find the rocket in a field.

    What that meansA GPS tracker works out where it is from satellites and reports it. Giving it its own battery is what lets it carry on if everything else stops.

  2. Payload bay

    The engraved plate, carrying the name of everyone who helped build this.

    What that meansEngraved means the names are cut into the plate, so they stay legible.

  3. Recovery

    Drogue at apogee, main canopy low down, fired by a commercial altimeter with its own battery and its own pyro channels. Nothing safety-critical touches the Pi.

    What that meansApogee is the highest point of the flight. A drogue is a small parachute that comes out there, and the main canopy is the large one that opens lower down. An altimeter is the instrument that decides when, and a pyro channel is an output on it that fires a small charge to release a parachute. Keeping all of that on a separate unit, with its own battery, is what “nothing safety-critical touches the Pi” means.

  4. Avionics bay

    A Raspberry Pi 4B running a real mail server: its own domain, its own DKIM key, an SMTP daemon and a LoRa radio. This is the part nobody has flown before.

    What that meansA Raspberry Pi is a small single-board computer. A daemon is a program that keeps running in the background, so an SMTP daemon is the part that answers mail connections. DKIM is a digital signature added to each message, checked against a public key published in DNS, so the receiver can tell the message really came from that domain. LoRa is a radio technique built for sending small packets a long way on little power.

  5. Fin can

    Four swept fibreglass fins and the motor mount. Fibreglass, not carbon. Carbon would turn the airframe into a Faraday cage and the radio would never be heard.

    What that meansA Faraday cage is an enclosure made of conducting material that blocks radio. Carbon fibre conducts electricity, so a carbon airframe would act like one around the antenna. Fibreglass does not, and that is the whole reason for the choice.

Specification

The numbers, one by one.

Eight lines of specification, each with a short note on what it tells you.

Height
1.80 m

The height of the whole rocket, nose to tail.

Diameter
mm

The width of the rocket.

Airframe
Fibreglass

Chosen so the radio can be heard.

Motor
mm reloadable

The motor is 38 mm across, and a reloadable one has a casing that is used again.

Target apogee
ft

The height the flight is aiming for. About 914 metres.

Recovery
Dual deploy

Two parachutes: a drogue at the top, a main lower down.

Downlink
LoRa,MHz

The radio link from the rocket to the ground station.

Payload
Raspberry Pi 4B

The computer that runs the mail server.

Words on this page

A short glossary, in plain English.

You do not need to know any of this to enjoy the idea. If you want to, here is every term the page uses.

Apogee
The highest point of a flight.
Altimeter
An instrument that measures height. Here, a commercial one decides when the parachutes come out.
Authoritative DNS
The server that holds the official DNS answers for a domain.
Daemon
A program that keeps running in the background, waiting for work. An SMTP daemon waits for mail connections.
DKIM
A digital signature added to a message and checked against a public key published in DNS.
DMARC
A DNS record telling receivers what to do with mail that fails authentication, and asking them to send reports.
DNS
The lookup system that turns a domain name into records: where its mail goes, who may send for it.
Drogue
A small parachute that opens first, at the top of the flight.
Dual deploy
Recovery in two stages: a drogue at apogee, then the main canopy low down.
Faraday cage
An enclosure of conducting material that blocks radio waves.
Inbox placement
Which folder a message lands in: the primary inbox, another tab, or spam.
LoRa
A radio technique for sending small packets a long way on little power.
Mail client and mail server
A client is the app you write in. The server is the program that talks to other servers and moves the mail. Until now, flying mail has meant a client in the air and a server on the ground.
Main canopy
The large parachute that opens low down.
Pyro channel
An output on an altimeter that fires a small charge, used to release a parachute.
Relay
A middle step that carries a message part of the way. This flight has none on the ground.
Reloadable motor
A motor whose casing is used again, with a fresh charge loaded for each flight.
Seed mailbox
A mailbox set up only to receive test messages, so you can see where they land.
SMTP
The language mail servers use to hand a message to each other.
Where the rocket meets the product

Playful on top, the product underneath.

Warmerly is email warmup and cold outreach software. The rocket is the playful part, but the things it will do are things the product already does for every sending domain.

Email warmup

Threaded warmup emails with other mailboxes, automatic replies, junk-folder rescue, and a daily limit that rises gradually. The rocket's launch is measured in warmed emails.

Read more →

Inbox placement

Placement tests show which folder a test message reached, as a guide for now.

Read more →

Deliverability monitoring

SPF, DKIM, DMARC, MX and TLS re-checked every day, each with the fix rather than the error code. A flying domain is still a domain.

Read more →

Also see DMARC monitoring and how Warmerly works.

Questions

Questions about the rocket.

What is the Warmerly Rocket?

Mk-I, build 001: a rocket with a mail server bolted into the airframe. On the way up, the server opens an SMTP connection, signs a message with its own DKIM key, and delivers it, from the air, over radio, with no relay on the ground.

When does it launch?

At one million emails warmed. This page gives no date and no running count, only what the project is and what will fly.

Hasn't someone already sent email from a vehicle?

Yes, and we say so. Astronauts have sent email since 1991, Shannon Lucid and James Adamson, from Atlantis on STS-43. The ISS has had email for decades. But every one of those messages was sent by a client talking to a mail server on the ground.

So what is new?

Nobody has flown the server itself. Shuttle, station, weather balloon and aircraft all relayed. That is the part we are going after.

Does anything on the ground carry the mail?

No. The Pi holds the SMTP connection itself. The ground station is a radio modem, not a relay, and it forwards packets and nothing else.

Is the recovery system tied to the mail server?

No. Recovery is fired by a commercial altimeter with its own battery and its own pyro channels. Nothing safety-critical touches the Pi.

How will you find it after it lands?

A GPS tracker in the nosecone, on its own battery, chirps its position once a second. It has to keep working if everything else stops, because this is how we find the rocket in a field.

Why fibreglass and not carbon?

Carbon would turn the airframe into a Faraday cage and the radio would never be heard.

What is on the engraved plate?

It carries the name of everyone who helped build this. It sits in the payload bay.

Has any of this been done before?

As far as we can establish, none of the four things has. We can't prove a negative, so if you know otherwise, tell us and we'll say so on this page.

What has a rocket got to do with email warmup?

The inbox-placement test it will run is the same one the product runs. The message it sends is signed with its own DKIM key, as the mail of any properly set up sending domain is. And the launch itself is tied to the product by a number: one million emails warmed.

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