# svcadm disable smtp:sendmail
# cd /lib/svc/method
# cp smtp-sendmail smtp-sendmail.orig
# {Editor} smtp-sendmail <- use your Editor Program.

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Find
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$SENDMAIL $MODE -q$QUEUEOPTION$QUEUEINTERVAL $OPTIONS &  
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Modify
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OPTIONS="-OPrivacyOptions=noetrn -ODeliveryMode=queueonly -OQueueDirectory=/var/spool/mqueue.in"
$SENDMAIL $MODE -q$QUEUEOPTION$QUEUEINTERVAL $OPTIONS &
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Save
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# svcadm enable smtp:sendmail