|You can quite safely set your list to release at Midnight.  Usually
LISTSERV takes not more than about 5 minutes to send out digests and then
will do the list mail in proper turn.

And just to be pedantic, just because LISTSERV(R) sends it out does NOT
mean it is delivered to the intended recipient soon thereafter, though
hopefully that does occur.

It is my understanding that most MTA clients will retry at most twice per
hour if the MTA server is unavailable.  or put a different way, *I* would
not want to bet my life or business on the timely delivery of email.

/Pete