Statistical information in syslog

* Statistics par transaction

(v+w+x+y/z)	v: number of recipients with success
		w: deferred recipients
		x: number of failure on DNS lookup (host unknown)
		y: number of failure on SMTP (user unknown)
		z: number of total recipients
relay=		destination MX host (IP address if known)
to=		recipients to be sent to the MX host
proto=		ESMTP features supported by the MX host
delay=		time taken for delivery to the MX host
code=		final response code from the MX host (accept message)

* Summary statistics

ENVID           Envelope identifier passed as ENVID= parameter in ESMTP.
                (This may not be same as queue-id by sendmail.)
nquery=		number of DNS answers / number os DNS queries
nconnect=       connections with success (processed successfully to QUIT
		command) / number of connect() to be tried
ntimeout=       number of connections which required timeout operation.
ntrans=         transactions with success / prepared transactions
                counted up multiple times even if same connection is used.
nsent=          recipients with success / number of all recipients
ndeferred=	recipients with temporary failure
nerror=         addressing error on DNS lookup (e.g. host unknown)
                + addressing error on SMTP (e.g. user unknown)
dnsmaxcq=	max number of concurrent DNS query
maxsock=        max socket number to be used.
tmx=            time taken for MX lookup
tdelivery=      time taken for 90% delivery with SMTP / time taken for
		complete delivery with SMTP (after completion of MX lookup)
maxdelay=       time for longest SMTP transact
tdelay=         total time by smtpfeed processing
tsendmail=	time from start of sendmail till start of smtpfeed
dns_i/o=	total number of transfered bytes between DNS server
smtp_i/o=	total number of transfered bytes on input/output channel
		of SMTP
mem=		total size of memory allocated by malloc()
