>host -t mx example.com
;; connection timed out; no servers could be reached

> time echo "This is a test message" | /usr/lib/sendmail -ftest@test.com test@example.com
real 2m36.252s
user 0m0.004s
sys  0m0.005s

> grep resolver /etc/mail/sendmail.cf
Timeout.resolver.retrans=5s
Timeout.resolver.retry=4

timeout: n
    sets the amount of time the resolver will wait for a response from a remote name server before retrying the query via a different name server. Measured in seconds, the default is RES_TIMEOUT (see <resolv.h> ).
attempts: n
    sets the number of times the resolver will send a query to its name servers before giving up and returning an error to the calling application. The default is RES_DFLRETRY (see <resolv.h> ).