What an alias actually is

An alias is a real, working email address that belongs to you and forwards somewhere else. k7fq2m@alias.mom arrives here, we look up where it goes, and we pass it on to your actual mailbox.

The shop that has k7fq2m@alias.mom does not have your address. It cannot sell it, leak it, or hand it to whoever buys them next. If mail to that alias turns bad, you delete the alias and it stops. Nothing else you own is affected.

What happens to a message

1. Someone sends mail to your alias
2. Our server accepts it, checks the alias exists and is enabled, and checks the sender is not one you have blocked
3. We record a single line of metadata: which alias, which direction, whether it went through. No sender, no subject, no body
4. We rewrite the headers so your mailbox provider will accept it, and mint a masked reply address for that sender so you can write back without exposing yourself
5. We forward it, sign it with DKIM, and forget it

Step 5 is the part worth noticing. In forwarding mode nothing is stored. The message exists on our machines for as long as it takes to send it on.

The header rewriting, and why your mail looks slightly odd

Forwarded mail carries a From we have adjusted. This is not cosmetic. If we passed the sender's From through untouched while sending from our servers, your mailbox provider would see a message claiming to be from shop.com arriving from a machine shop.com never authorised, and it would go to spam or be rejected outright. That is SPF and DMARC doing their job.

So we rewrite it. The sender's real address stays visible in the display name, and the Reply-To points at their masked address so replying does the right thing.

We also strip the Received chain, which normally records every server a message passed through, because it would otherwise tell your mailbox provider and anyone reading the headers rather a lot about where you are.

What we do not do

We do not scan message content. Not for advertising, not for "features", not to train anything. The privacy page lists every table in the database and what is in it, and a test fails the build if a new one appears without being added to that list.

Next

Make one, or read about the forwarding-or-inbox decision first, since it changes how the rest of this works.

Something here wrong or missing? Tell us. These pages live in the same repository as the code, so a correction is a one-line change.