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How can we improve Proton Mail or Calendar?

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Improve Default Address Handling for Forwarded/BCC Emails

Currently, the "Default Address (Custom Domain)" works only when emails are sent directly to it or to linked catch-all addresses. If the domain's MX does not point to Proton (e.g., it points to a forwarding service), Proton uses the actual recipient address (usually @proton.me) instead of my Default (Custom Domain) address when replying.
Note: In this scenario, it does not work even if the Custom Domain address is already set as the Default.

Example: domain.com points its MX to a mailing list, which then forwards emails to my @proton.me and @gmail.com mailboxes. When a sender emails to @domain.com and the message is forwarded to my @proton.me address, I can't automatically reply using my Default Address (@domain.com). I must manually switch the From address from @proton.me to @domain.com.

I suggest adding checks for forwarded and BCC emails (i.e., in scenarios where "Header To ≠ RCPT TO"):

  1. If "Header To ≠ RCPT TO", check whether the Header To address matches the user's Default Address.

  2. If yes, use the Default Address when replying; otherwise, follow the existing Reply logic.

This ensures that replies consistently use the user's Default (Custom Domain) Address even for forwarded and BCC emails.

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  • haiku5432 commented  ·   ·  Report

    I use proton mail as unified front-end for a couple of mail domains hosted elsewhere.

    One is hosted by Google Workspace. This works great:

    DNS: customdomain-1.example -> MX points to google, SPF/DKIM allows both google and proton as sender

    Proton's OAuth app is installed into Google Workspace. Messages show up in proton and replies use the expected FROM address.

    However, with a local small-business email provider this doesn't work so great:

    DNS: customdomain-2.example -> MX points to indie provider, SPF/DKIM permits both indie provider and proton

    Proton will do one-time imports, but there's no 'permanent' IMAP harvest. So instead, the email address is configured as a forward on the other end: no mailbox, no storage. Indie provider receives mails, and forwards them to proton (on a third custom domain, fully and only linked to proton). The forwards contain valid ARC Chain headers and all that.

    When I click reply on these messages, the FROM is set to that third domain. I'd want to use the original domain instead. I can choose it manually, but I want it to be associated by default.

  • Hugo Logmans commented  ·   ·  Report

    Scanning through the open requests, there are more places where this account selection problem occurs, like forwarding to extra recipients.

  • Hans Caspers commented  ·   ·  Report

    There is no reason that this should not be supported. If sending by default from a custom domain without MX pointing to Proton is supported, replying and forwarding should also allow the sender address to be that custom domain.

    Please fix this as it is really an unnecessary but highly annoying 'bug'.

  • John Erik Setsaas commented  ·   ·  Report

    Currently, I have for EVERY email I reply to, verify that the sender is set correctly to the email to which it was sent.

    This should be a very simple UX feature to implement. Please put priority on this.

    Thank you.

Proton Mail & Calendar: Changes to existing features

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