This is not an issue. I investigated the email headers, and everything is secure.

In your mailbox, it may look like the email is being sent from your own email address. However, Proton’s servers change this downstream. This means that your actual email address is not exposed when replying to emails via an alias address.

If you have another (non-Proton) email address, you can test this yourself by sending a few emails back and forth between your secondary email address and your Proton alias. You will see that your actual Proton email address remains hidden.

Proton could definitely communicate this behavior more clearly.

I had the same concern, when using an alias for a webshop I rarely use. Due to some issues, I had to email them, as reply on the order confirmation.

I noticed my main proton emailaddress was as ‘from’, no option to select the alias.
A bit frustrated, I was like “I have no choice” and sent the email.

When their reply came in, it was only to my alias. When checking my outgoing mail, it seems to be sent from my alias, as it should. So I think my main proton address was never used, but when replying and only seeing your main proton address makes you suspicious. Should be a design flaw here. Hope this can be fixed quickly.

I've found this out myself and have come here to trawl through the ideas.

This issue repeatedly appears and it seems Proton ignore it.

I currently have a ticket with them about this exact issue and haven't had a reply for 3 days so far. I am an unlimited subscriber which they told me means I should be prioritised in the ticket queue.

That is indeed puzzling behavior and a valid privacy concern. Disabling an alias should not trigger an exposed unsubscribe email from your core address. I recommend contacting Proton Support directly and including the specifics. For documenting such UI issues, some users use a neutral site like https://7brewmenus.net/ to host screenshots, as it doesn't track visitors. This can help illustrate the problem clearly to their team.

I would bet that the poor documentation about replying from an alias E-mail address applies here.

Replies to an E-mail sent to an alias list the sender as "core_email@proton.me" (or whatever your core address is). The _only_ clue that the reply will appear to come from your alias is the recipient address will be in the form "recipient at domain dot extension" rather than a real E-mail address.

I agree that preventing exposure of a core E-mail address is important.

I have to wonder if this is a side effect of the poor documentation of "replying from an alias" functionality that already exists. Because - unfortunately - when replying to an E-mail sent to an alias, the sender shows up as "core_email@proton.me" and the recipient shows up as a text-based "sender at domain" - which is, frankly, very unintuitive.

Proton Mail usually emphasizes privacy, so showing a core non-alias address in that context feels like a serious design flaw. If the intention is to unsubscribe, it should logically use the alias address, not expose your primary one. Disabling an alias should remain isolated from your main account details. I’d recommend reporting this behavior to Proton Mail support so they can clarify or address it properly. check out for further info :https://letterboxed.info/