Postfix auto start on Sierra for smtp relay
To get this working on Sierra you have to modify the existing launch daemon slightly:


Disable SIP
Modify /System/Library/LaunchDaemons/com.apple.postfix.master.plist:

sudo nano /System/Library/LaunchDaemons/com.apple.postfix.master.plist


remove the lines:

&lt;string&gt;-e&lt;/string&gt;
&lt;string&gt;60&lt;/string&gt;


add the lines:

&lt;key&gt;KeepAlive&lt;/key&gt;
&lt;true/&gt;


save the file and exit nano
Reload the launch daemon:

sudo launchctl unload /System/Library/LaunchDaemons/com.apple.postfix.master.plist
sudo launchctl load /System/Library/LaunchDaemons/com.apple.postfix.master.plist

Enable SIP