On macOS 13.1 (Ventura) I have an Apple Mail rule that is setup to Forward a received email to a specific email address. In addition to forward, it will set the color of the message.

I have tested the rule, and the message color is set, confirming the rule is firing, but it will not forward the email. I have tried to use Forward, Forward with Message, and Redirect. None of these options will result in the email being sent to the designated address. I also tried different addresses, but still no luck.

I am using Proton Mail in this case, but I tried using Gmail instead and it works fine. So, it appears to be related to the use of Proton Mail, but I can't be certain.

For those who aren't familiar with Proton Mail, they don't support email forwarding on their server and they require the use of a IMAP proxy app they call Proton Bridge, which encrypts and decrypts messages from an IMAP email client to the Proton Mail service.

Has anyone been able to get an email forwarding rule to work in Apple Mail and if so, anyone done so with Proton Mail?

  • Can you forward a message to the Proton address by hand?
    – Barmar
    Commented Apr 27, 2023 at 23:08
  • 2
    Mail.app doesn't know anything about the type of system it's forwarding to. If the message isn't going through, the problem is most likely at the receiving end, or a problem between your ISP and the destination server.
    – Barmar
    Commented Apr 27, 2023 at 23:11
  • Mail isn’t going to be able to discriminate between sending a message and sending a forwarded message; a “send” is a “send” as far as it’s concerned. This might be something you need to set up a server side rule for.
    – Allan
    Commented Apr 27, 2023 at 23:30

1 Answer 1


As it turns out, the reason the mail was not being forwarded is the port number on my outgoing SMTP server was wrong. However, there were no errors to indicate this; Apple Mail just failed silently. Once I updated the SMTP port, the mail forwarded fine.

It's worth noting that one still cannot Redirect mail via Apple Mail if using Proton Mail.

  • Nice find. I wonder if Connection Doctor in Apple mail shows things correctly with the correct port and then if you "break it again" to test, connection doctor shows the failure.
    – bmike
    Commented Jan 23 at 19:06

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