I did a
#sendmail -Ac -v -q
and received this response
Running /var/spool/clientmqueue/mA55486v005844 (sequence 1 of 2)
u.com.my: Name server timeout
xxx@x.com.my... Transient parse error -- message queued for future delivery
Running /var/spool/clientmqueue/mA4A10Gm004805 (sequence 2 of 2)
u.com.my: Name server timeout
xxx@x.com.my... Transient parse error -- message queued for future delivery
u.com.my: Name server timeout
xxx@x.com.my... Transient parse error -- message queued for future delivery
There is no DNS server configured.
root@xxxx $ nslookup mailserver
;; connection timed out; no servers could be reached