I know we already exchanged some emails on this, but for the sake of others who may run into this:
I think you've made your postfix settings too restrictive.
May be OK for the service that accepts emails "from the outside" and destined for your domain, but there is really no reason to enable it for the service that accepts emails from one of your own accounts ...
... because "accepting emails from one your own accounts" should use authentication for protection (unless you're interested in running an open relay).
This is from my Postfix config ( version 2.11.3-1+deb8u2 on Debian 8 )
smtpd_client_restrictions=permit_sasl_authenticated,reject
Aqua Mail (or other email apps that you may use to send from *your* account or *an* account) will authenticate - i.e. log into your (or some other) account and therefore will fall under permit_sasl_authenticated and won't be rejected.