unable to send mail through php mail function on CentOs (Amazon EC2)

$ service sendmail status

sendmail dead but subsys locked

sm-client (pid  17067) is running...

$netstat -lnp | grep :25

tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN      1057/master

$ kill -9 1057

$ rm /var/lock/subsys/sendmail

$service sendmail stop

$service sendmail start

$service sendmail status

sendmail (pid  17288) is running...

sm-client (pid  17296) is running...