[ic] Some emails can't be sent - could this be why ? AHA (maybe)

[Jeff Dafoe]

> Seems to me that having a dead box listed as the first nameserver in
> /etc/resolv.conf could easily hurt sendmail's performance. Do you guys
> think this is a likely explanation of my problem? I suppose time will
> tell but I'm interested in your opinions.

    Yes.  The issue is that the amount of time it takes most resolver
libraries to figure out that the primary is down and switch to the secondary
seems to be greater than the amount of time most applications use for their
hostname resolution timeout.  But only by a slight amount, thus creating the
type of intermittent issues you experienced.
    This must've killed your web server performance too, assuming that
hostnamelookups are on (as is required for interchange prior to
4.9.reallyrecent).

Jeff