Today, I noticed many entries in the log of my mail server with this error:

   warning: connect to 127.0.0.1:60000: Connection refused

The fact is that this does not tell you anything (duh!)

We use postfix which runs many servers and each server talks to the other via network messages. Up to here, nothing special. The problem is whenever a server cannot connect to another, instead of telling us who, what, when, it just tells us that the connection did not happen (although there is the date, but it does not tell you when in the chain of events.)

This specific error, which looks like the system attempts to connect using IP v6 (although it is really an IP4 + port).,appears whenever Postgrey is not running.

Restarting postgrey solved the problem at once and I started receiving emails again.