How can I use the Postfix setting always_bcc to forward mail for archiving purposes?

[matrixes]

I have a need to send a copy of all incoming emails to my instance of docker-mailserver, to an address on the same instance.

I have done the following in an attempt to accomplish this (I'm using dummy mail accounts in this example):

1. I set up the following email accounts

• [email protected]
• [email protected]
• [email protected]

2. I edit the file "docker-data/dms/config/postfix-main.cf" and add the line [email protected]
3. I restart docker-mailserver (the logs do not complain about anything out of the ordinary)
4. I send an email to [email protected]

I assumed a copy would automatically be sent to [email protected], but unfortunately nothing is received, and I can't really get to grips of where I'm misunderstanding the outcome.

Any help would be appreciated. :)

[polarathene]

3. I restart docker-mailserver (the logs do not complain about anything out of the ordinary)

How did you restart? postfix-main.cf is only applied on container creation (initial setup).

I have attempted to reproduce but everything appears working to me, so I will assume you did not restart your DMS container correctly (as we document in red at the start of our troubleshooting page).

Here is a complete compose.yaml that you can copy/paste and run.

services:
  dms:
    image: ghcr.io/docker-mailserver/docker-mailserver:${DMS_RELEASE:-15.1.0}
    hostname: mail.example.test
    # These ENV are only to optimize the reproduction time:
    environment:
      # Amavis has some added overhead in startup and extra processing when mail arrives, disable:
      ENABLE_AMAVIS: 0
      # Trusting any client connection coming from within the container itself:
      # (Delay appears to be about 6 seconds by postscreen upon receiving a connection from swaks, according to /var/log/mail.log)
      PERMIT_DOCKER: container
      # Avoid a startup delay caused by checking for new DMS release to notify by a mail sent to postmaster
      # (which would have failed as postmaster is not configured either)
      ENABLE_UPDATE_CHECK: 0

    # The Docker Compose `configs` feature is a way to embed files into `compose.yaml`
    # This is only used to bundle the whole example into a single `compose.yaml` file for reproductions
    # Normally you'd prefer to use `volumes` instead with external files.
    configs:
      - source: dms-accounts
        target: /tmp/docker-mailserver/postfix-accounts.cf
      - source: dms-postfix-overrides
        target: /tmp/docker-mailserver/postfix-main.cf
      - source: test-bcc-works
        target: /usr/local/bin/test-bcc-works
        mode: 0755

# NOTE: In `compose.yaml` a `$` indicates a variable to replace with a host ENV value
# The content below contains `$` chars, which are escaped as `$$` to prevent being interpolated as ENV.
configs:
  dms-accounts:
    content: |
      [email protected]|{SHA512-CRYPT}$$6$$sbgFRCmQ.KWS5ryb$$EsWrlYosiadgdUOxCBHY0DQ3qFbeudDhNMqHs6jZt.8gmxUwiLVy738knqkHD4zj4amkb296HFqQ3yDq4UXt8.
      [email protected]|{SHA512-CRYPT}$$6$$sbgFRCmQ.KWS5ryb$$EsWrlYosiadgdUOxCBHY0DQ3qFbeudDhNMqHs6jZt.8gmxUwiLVy738knqkHD4zj4amkb296HFqQ3yDq4UXt8.

  dms-postfix-overrides:
    content: |
      [email protected]

  test-bcc-works:
    content: |
      #!/usr/bin/env bash

      # Our test email that should also be received at our bcc-receiver mailbox:
      swaks --silent --server localhost --from [email protected] --to [email protected] --body 'hello world'

      # Allow a buffer of time to process mail by Postfix + Dovecot after swaks completes the delivery:
      sleep 3

      # Helper function for testing convenience:
      function verify_mail_received_for() {
        local RECIPIENT=$${1}

        echo -e "\nChecking recipient: $${RECIPIENT}"

        grep 'mail postfix/lmtp' /var/log/mail.log | grep --fixed-strings --silent "to=<$${RECIPIENT}@example.test>, relay=mail.example.test[/var/run/dovecot/lmtp]"
        local POSTFIX_SENT=$${?}

        grep 'mail dovecot' /var/log/mail.log | grep --fixed-strings "dovecot: lmtp($${RECIPIENT}@example.test)" | grep --fixed-strings --silent "stored mail into mailbox 'INBOX'"
        local DOVECOT_RECEIVED=$${?}

        if [[ $${POSTFIX_SENT} -eq 0 && $${DOVECOT_RECEIVED} -eq 0 ]]; then
          echo 'Delivery successful'

          # Outputs the number of mails in the mailbox accounts inbox:
          doveadm mailbox status -u "$${RECIPIENT}@example.test" messages INBOX
        else
          echo 'Delivery failed'
        fi
      }

      echo 'Checking inboxes for received test mail...'
      verify_mail_received_for john.doe
      verify_mail_received_for bcc-receiver

With the above compose.yaml you can then run the following command, and get the output showing it was successful:

# DMS may take about 5-10 seconds to start depending on host system:
$ docker compose up -d --force-recreate && sleep 10 && docker compose exec -it dms test-bcc-works

Checking inboxes for received test mail...

Checking recipient: john.doe
Delivery successful
INBOX messages=1

Checking recipient: bcc-receiver
Delivery successful
INBOX messages=1

[matrixes]

I tested your suggestion and it does indeed look like I can reproduce your results. As in, when running your suggested commands, I get similar output as yours.

However, after having configured [email protected] in "docker-data/dms/config/postfix-main.cf" in my own docker-mailserver setup, I have started getting duplicate emails sent to the corresponding catchall address when emails are received.

This got me thinking that it could have something to do with my current configuration in terms of aliases? I have a number of "catchall@[domain(s)]" aliases that worked just fine before adding the always_bcc to "postfix-main.cf".

My "postfix-virtual.cf" file looks like the following (and this has been working very well for my purposes thus far, before this new venture of bcc:ing everything for archiving)

...
[email protected]  [email protected]
[email protected]  [email protected]
...
[email protected]  [email protected]
[email protected]  [email protected]
...
@example.com  [email protected]
@example2.com  [email protected]
...

I'm speculating that the emails that are supposed go to "[email protected]" are caught in the catchall rules.

I have made a feeble attempt of adding [email protected] [email protected] before the @example.com [email protected].
Unfortunately this has only resulted in receiving only one email to the intended recipient, and no bcc copy being sent/created to the "bccreceiver" address.

If it's still unclear where the issue may be, I'll attempt at a more complete post that if nothing else could give a more complete view of my current setup.

[matrixes]

Eureka! I re-reviewed my configuration and noticed that there was an error in "postfix-virtual.cf"

Before:

...
[email protected]
[email protected]  [email protected]
[email protected]  [email protected]
...
[email protected]  [email protected]
[email protected]  [email protected]
...
@example.com  [email protected]
@example2.com  [email protected]

After:

...
[email protected]  [email protected]
[email protected]  [email protected]
[email protected]  [email protected]
...
[email protected]  [email protected]
[email protected]  [email protected]
...
@example.com  [email protected]
@example2.com  [email protected]

Having done this, everything seem to work as I would expect. Mail is handled as before and there is an additional copy sent to "[email protected]"

Thanks for the example @polarathene . You've shown me a few tricks with Docker that I haven't seen before, which will be very valuable in the future.