Hello World

pop3_logout_format = top=%t/%p, retr=%r/%b, del=%d/%m, size=%s

%i - total number of bytes read from client
%o - total number of bytes sent to client
%t - number of TOP commands
%p - number of bytes sent to client as a result of TOP command
%r - number of RETR commands
%b - number of bytes sent to client as a result of RETR command
%d - number of deleted messages
%m - number of messages (before deletion)
%s - mailbox size in bytes (before deletion)
%u - old/new UIDL hash. may help finding out if UIDLs changed unexpectedly