Public alpha
Forward an email to a time.
Forward a booking to 3d@mailwhen.com and it is back in your inbox in three days, thread and attachments intact. Nothing to install, no dashboard to check, nothing to sign in to. The address is the whole product.
Works with the email you already have. Sign up by sending one message.
How it works
Three steps, and you only do the first.
Everything happens in the email app you already use. MailWhen never asks you to go anywhere else.
Forward it
Send any email, forwarded or freshly written, to an address that says when you want it back: 45m@, 3d@, friday@. To, Cc and Bcc all work.
Forget about it
That is the end of your involvement. Nothing to confirm, nothing to check on. Put the address in Bcc and nobody else on the thread ever knows a reminder exists.
It comes back
Right on time, the original lands in your inbox with its subject, message and attachments intact, in the conversation it came from.
The addresses
A language you already speak.
Nothing to learn beyond a number and a letter. MailWhen understands a fixed set of addresses and nothing else, so it never guesses at what you meant and cannot invent a reminder you did not ask for.
| Send it to | Anything from | And it returns |
|---|---|---|
| 15m@ | 1m – 90m | In fifteen minutes, to the minute. |
| 2h@ | 1h – 48h | In two hours. |
| 3d@ | 1d – 31d | In three days, at this time of day. |
| 2w@ | 1w – 52w | In two weeks. |
| 6mo@ | 1mo – 48mo | Six months later, on the same date. |
| 1y@ | 1y – 25y | A year from today, on the same date. |
| tomorrow@ | — | Tomorrow morning at 6:30. |
| friday@ | any day | The next Friday, at 6:30 AM. fri@ also works. |
| weekly@ repeats | — | Every week, on the day you sent it. |
| monthly@ repeats | — | The same date each month. |
| each-friday@ repeats | any day | Every Friday, until cancelled. |
| january@ | any month | The next 1 January, at 6:30 AM. jan@ also works. |
| 5am@ | 1am – 11pm | The next five in the morning. 12am@ is midnight. |
| each-5am@ repeats | any hour | Every morning at five, until cancelled. |
| cancel@ | — | Forward a repeating reminder here to end it. |
| list@ | — | Send an empty message here to be told what is pending. |
Shown in your device’s timezone. Your reminders follow your account’s timezone: new accounts start on US Central time, and a message to tz-europe-london@mailwhen.com — or whichever zone is yours — changes it.
What returns
Your own email, returned to you.
Not an alert about a message, and not a link to somewhere else. The message itself, delivered to the place you were always going to look.
- Scheduled with
- 3d@mailwhen.com
- Originally sent
- Mon, 24 Aug, 9:14 AM
- Status
- OK
Check in for this.
Your booking is confirmed. Reference QK4-8812…
- It arrives where you expect In the same conversation it left, so the thread continues from where you set it aside rather than starting again elsewhere.
- Attachments come with it Files and inline images are carried across intact. Where something is too large to include, the reminder states so rather than omitting it silently.
- Every reminder reports its own condition A single line confirms the message arrived complete, or names exactly what did not. You never have to wonder whether you are looking at the whole message.
- You decide who else is reminded Bcc a MailWhen address and the reminder is yours alone: nobody else on the message is contacted, and nobody learns a reminder exists. Put it in To or Cc, where everyone can see it, and anyone on the thread who also uses MailWhen gets the reminder too. If somebody could not be included, you are told.
Scope
What it won’t do.
A short list, and a deliberate one. Knowing where a service stops is as useful as knowing what it does.
It is not a mailbox
MailWhen does not forward your mail, reply on your behalf, or hold messages for anyone else. The only message it will ever send you is the one you sent it.
Only you can use your account
Every message is checked to make sure it really came from your address before anything is scheduled. Knowing a MailWhen address does not let anyone else use your account.
One-off reminders cannot be recalled
Repeating reminders arrive with a way to stop them. A one-off 3d@ does not, so cancelling one before it lands means writing to hello@mailwhen.com. Rare, but worth knowing in advance.
A mistyped address is never silent
You get a short note naming what was not understood, along with the addresses that are valid. Nothing is lost, and any valid address on the same message is still scheduled.
Reliability
A reminder that never arrives is the only failure that counts.
Most of the engineering goes into detection rather than into features. You are trusting MailWhen with something you have deliberately stopped thinking about, and that only works if it is dependable enough to forget.
It verifies itself hourly
Every hour, MailWhen sends itself a live reminder through the same path yours takes and confirms its return. A fault anywhere along it raises an alarm within a few hours — found by the service, rather than by you noticing a reminder that never came.
Inactivity raises an alarm
Services of this kind rarely fail loudly. They stop, and no one notices until something that should have arrived has not. MailWhen is monitored for inactivity as closely as it is for errors.
Your mail cannot be lost in error
No part of the system has the ability to delete a message you have sent it. Stored copies expire on a fixed schedule and by no other means, so no fault can remove one early.
Sent twice, delivered once
Email is routinely retried and duplicated in transit. MailWhen is built for it: the same message arriving twice produces a single reminder, because a duplicate is its own kind of failure.
Get started
Sign up by sending an email.
There is no form and no password. The first time you write to MailWhen it replies once, asking you to confirm it really is you. Reply, with nothing typed, and your account exists.
- Forward an email to 3d@mailwhen.com, or send a blank one to register@mailwhen.com.
- Reply to the confirmation that comes back. Nothing to type.
- Send your reminder again. The message that started things is not turned into one.
MailWhen replies only when it can verify that the message came from your address, which nearly every mail provider makes automatic. If nothing arrives within a few minutes, check junk or quarantine for a message from register@mailwhen.com. Still nothing? Write to hello@mailwhen.com and a person will set you up.
MailWhen is in public alpha. It is free while it lasts, it has been in daily use since August 2026, and it is still being shaped, so rough edges and questions both go to hello@mailwhen.com.