Some time back I created a GitHub repository to contain the changes I make to the distributed Sympl Exim4 and Dovecot systems. These changes are not new, started life on a Symbiosis system and are intended to provide better security and report things to the firewall. They will work on any Sympl system, assuming you’ve not made any changes.
I’ve now revised this to include an installation script that installs the new files and edits the two files that need altering. I’ve also removed the parts of the Sympl distribution that are not changed, which I think was an error to include in the original distro.
The installation script is configurable so you don’t have to buy into all the changes if you don’t want to.