I have the same issue, but there is a partial workaround. After debugging (and a support ticket with Proton), I found that Proton was using the envelope recipient used by bcc (shown in Proton as the 'X-Original-To' header) as one of the candidates, in addition to all the Cc and To headers. You can re-order the identities, and the first one that matches any of the To/Cc/X-Original-To headers will be the one selected as the From address. So put the proton address last in the list, and it will prefer your other addresses. This unfortunately does not work for the catchall.
I would love if the default address was used when the catchall matches, even over the envelope recipient. Right now, if you use a catchall with an email forwarder, it will always go to the forwarded address instead of the original address.
Robin
I have the same issue, but there is a partial workaround. After debugging (and a support ticket with Proton), I found that Proton was using the envelope recipient used by bcc (shown in Proton as the 'X-Original-To' header) as one of the candidates, in addition to all the Cc and To headers. You can re-order the identities, and the first one that matches any of the To/Cc/X-Original-To headers will be the one selected as the From address. So put the proton address last in the list, and it will prefer your other addresses. This unfortunately does not work for the catchall.
I would love if the default address was used when the catchall matches, even over the envelope recipient. Right now, if you use a catchall with an email forwarder, it will always go to the forwarded address instead of the original address.