speed improvements:
	connection failure history (inter-process)
	even MX-preference selection by history
	connection caching (inter-transaction, inter-process)
	parallelization of getting MX and SMTP
	option q: quick start
	daemonize
	address sorting (on over 100 recipients) when default relay is defined

operational:
	AAAA query cay be ignored? if ANY query contains MX and A, or if
	 additional answer for MX query contains A.
	TCP DNS query
	return information about issued SMTP command on error condition
	 (LMTP data response)
	changing envelope-from par recipient for errornous destination 
	 distinction (like "qmail")
	configuration of alias names for the host (refering $=w of sendmail.cf)
	IPv4/v6 address ordering par domain

protocol (known bugs):
	8bitMIME management
	DSN notification...

reliability:
	checkpointing

configure:
	static link required?
