escape the brackets in insert statement.

INSERT INTO SendMailDetails \(acctno, salutation, name\) values \('$acctno','$salutation','$name'\);

Not sure how it is going to work. You need to use sqlplus -s and here document <<EOF and EOF to make the interactive things work..

sqlplus -s username/password@connectstring <<EOF
INSERT INTO SendMailDetails (acctno, salutation, name) values ('$acctno','$salutation','$name');
commit;
exit;
EOF