I was fighting with this error for some time. I’ve fixed it quite a few times, but I forgot again because it’s been so long since I built a new mailscanner / mailwatch machine.

The error was this –

mailwatch detail.php XML-RPC Error: Invalid return payload:

And then in the logs some of this –

XML-RPC: xmlrpc_server::service: http headers already sent before response is fully generated. Check for php warning or error messages

mailwatch http headers already sent before response is fully generated. Check for php warning or error messages

Anyway, the fix was to create a php.ini file! Simples..

Simply put – cp /usr/local/etc/php.ini-production /usr/local/etc/php.ini && /usr/local/etc/rc.d/apache24 restart – fixed it for me! Hope it helps someone out there having xmlrpc problems with mailwatch

I’m running this with php56-5.6.17 and it works fine for me.