Sendmail and broken DNS

An ISP I use recently switched DNS servers and this, it turns out, broke sendmail.  Running

echo 'check_mail cfsc-bounces@computingfrontiers.org' | sdmail -d8.20 -bt

gave

dns_getcanonname(computingfrontiers.org, trymx=1)
dns_getcanonname: trying computingfrontiers.org. (AAAA)
        NO: errno=0, h_errno=1
dns_getcanonname: trying computingfrontiers.org.mscd.edu (AAAA)
        NO: errno=0, h_errno=1

which is not good.  Adding

O ResolverOptions=WorkAroundBrokenAAAA

to sendmail.cf fixed things

dns_getcanonname(computingfrontiers.org, trymx=1)
dns_getcanonname: trying computingfrontiers.org. (AAAA)
        NO: errno=0, h_errno=4
dns_getcanonname: trying computingfrontiers.org. (A)
        YES

The sendmail change notes say

New ResolverOptions setting: WorkAroundBrokenAAAA.  When
attempting to canonify a hostname, some broken nameservers
will return SERVFAIL (a temporary failure) on T_AAAA (IPv6)
lookups.  If you want to excuse this behavior, use this new 
flag.  Suggested by Chris Foote of SE Network Access and 
Mark Roth of the University of Illinois at
Urbana-Champaign.

which means someone will have to fix the DNS server...