Tagged addresses ([email protected])
Add +anything to your address and the mail still arrives, with the tag shown beside the sender. How to use plus addressing, and the four things it cannot do.
Your address accepts a tag. If you are [email protected], then [email protected] and [email protected] are also yours: the mail lands in your normal inbox, and the app shows the tag beside the sender so you can see which address it came in on.
There is nothing to switch on, nothing to register and no list to maintain. Any word after a + works the first time you use it.
How it works
Write your address, a +, and whatever you like:
| You hand out | Delivered to | Tag shown |
|---|---|---|
[email protected] |
[email protected] |
+shop |
[email protected] |
[email protected] |
+bank |
[email protected] |
[email protected] |
+a+b |
[email protected] |
[email protected] |
none |
The first + is the one that splits. Everything after it is the tag, kept exactly as it was typed. A + with nothing after it is simply your address with no tag.
This is the same convention Gmail, Fastmail and most other providers use, so a form that accepts a plus address elsewhere accepts one here.
Where you see the tag
Only when there is one. Untagged mail looks exactly as it always did.
- In the message list, a small
+shopchip sits beside the sender. - In the open message, the chip appears beside the
To:line on a computer, and beside to me on a phone.
Conversations are grouped by who wrote to you, not by which address they used. So if a shop writes to alice once and to alice+shop the next time, both messages sit in the same conversation, and the chip on each one tells you which address it arrived on.
What it is good for
- Finding out who leaked your address. Give each shop, forum or newsletter its own tag. When spam arrives at
alice+forum, you know where the address came from — see How to avoid spam. - Sorting by eye. The chip tells you at a glance that something came in on the address you only ever gave to one service.
- Keeping one address. You do not need a second account, and you do not have to change your real address when a tag starts attracting junk.
What it cannot do
Four honest limits. None of them is a bug, and knowing them in advance saves disappointment.
There is no "send as +tag". A reply to a message that arrived at [email protected] goes out from [email protected], so the other side learns your real address the moment you answer. If a tag needs to stay unknown to a correspondent, do not reply to it from here.
- A tag is not a secret. Anyone can read
alice+shopand work out thataliceis the real address. A sender who wants to defeat the tag only has to delete it. Treat it as a label, not as protection. - It is not a filter rule. The tag is shown; nothing is moved, flagged or filed automatically. Use folders and search for that.
- You cannot have a
+in your username. The character is reserved for exactly this purpose, which is also why no tagged address can ever collide with somebody else's account — see Change your username.
What our server sees
Cannot see
- The tag in any readable, stored form — your copy of the message keeps the original
To:line inside its encrypted headers, like every other header
Can see
- The recipient address, tag included, while an incoming message from outside is being delivered — the same as for any address on any mail system
Nothing is indexed by tag and no tag is written anywhere in the clear. The chip you see is drawn by your own device out of a header it had already decrypted.
The details
Tagged delivery is RFC 5233 sub-addressing. The address is split on the first +; the part before it is lowercased and matched against accounts, and the tag is carried through untouched. The split is applied to delivery questions only — who should receive this message — and never to identity questions: signing in, password recovery, choosing a username and checking whether a name is free all keep refusing a + outright, so a tag can never be used to impersonate an account or to claim one.
Because + is not a legal character in a username, no account name can ever be shadowed by somebody else's tag. The mail server is configured with recipient_delimiter = +, which is what lets system addresses such as postmaster+x resolve, but delivery itself does not depend on it: the full address including the tag is handed to the application, which does the split.
Any address that already delivers to your mailbox accepts tags, not just the main one.
Common questions
Do I have to create the tag first?
No. There is no list of tags anywhere. Invent one when you need it and it works immediately.
Does the sender see that it is a tagged address?
They see the address you gave them, which contains the +. There is no way to receive at a tagged address without the sender having it.
Can I turn tagged delivery off?
No. It is part of how addresses work here, as it is at most providers.
Does it work for chat?
No. Chat reaches people by their Private.Ki address itself; there is nothing to tag.
Is the tag case-sensitive?
The tag is shown as it was typed, so +Shop displays as +Shop. Delivery does not depend on its case.
Can two tags go to two different folders automatically?
Not today. The tag is displayed; filing is manual.