I have a postfix server that receives mail (authenticated) from several sources (scan-to-mail, apps and more) and based on sender address domainname relays that mail to several other servers (that handle the mailboxes of those domains). For the reason to let the mail there be dkim signed before it being send to the recipient's server if not delivered locally. One of those servers (Grommunio) only dkim signs authenticated mail for whatever reason. If tried changing its config to sign relayed mail also among other changes, but nothing works. Relayed mail doesn't get dkim signed, while mail from mailclients and webmail does get signed. So I need the relayed mail to that server to be authenticated. I've added "[server] user:password" in /etc/postfix/sasl_passwd but mail is still being relayed unauthenticated. What am I missing?
