Re: Struggling with DKIM signing

You defined a policy bank ORIGINATING but did not tell Amavis when to 
use it. A similar snippet is described in [1], where in addition to the 
policy bank definition, there is an interface_policy assignment for a 
dedicated inet_socket_port. You can use this port for a content_filter 
declaration in master.cf's submission service.

[1] https://www.ijs.si/software/amavisd/amavisd-new-docs.html