Re: virtual user list in a passwd file (without linux user)

Thanks again for your help. It is really appreciated.

Thanks for the reminder, I did implement the SPF part already.

So, I got it to work by following your suggestion (2).

I also changed a few things based on warnings I got in the logs and after more reading:

   /etc/aliases
      postmaster: root
      nobody: root
      "root@localhost": root
      # redirect all root mails to this:
      root: postmaster@site1.com

   /etc/postfix/main.cf
      # changed the following
      myhostname = mail.site1.com
      mydomain = site1.com
      myorigin = $mydomain

      # removed all domains that were already in virtual_mailbox_domains
      mydestination = localhost.$mydomain, localhost

      virtual_mailbox_domains = site1.com, site2.com, site3.com, mail.site1.com, mail.site3.com, mail.site2.com

Well it is only off-topic when your are an expert at both. In my case, I am not always sure if I have to change something in dovecot or postfix since they work together in my setup.

Now on to DKIM...