To setup an e-mail delivery using starttls and office365 e-mail, we have to edit 2 files:

    <bean id="reportSchedulerMailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl" lazy-init="true">
        <property name="host" value="${report.scheduler.mail.sender.host}"/>
        <property name="username" value="${report.scheduler.mail.sender.username}"/>
        <property name="password" value="${report.scheduler.mail.sender.password}"/>
        <property name="protocol" value="${report.scheduler.mail.sender.protocol}"/>
        <property name="port" value="${report.scheduler.mail.sender.port}"/>
        <property name="javaMailProperties">
            <props>
                <prop key="mail.smtp.sendpartial">true</prop>                     <----This line
                <prop key="mail.smtp.starttls.enable">true</prop>                 <----This line
                <prop key="mail.smtp.auth">true</prop>                            <----aaand this line
            </props>
        </property>
    </bean>

report.scheduler.mail.sender.host=smtp.office365.com
report.scheduler.mail.sender.username=source username in office 365
report.scheduler.mail.sender.password=source password in office 365
report.scheduler.mail.sender.from=from e-mail
report.scheduler.mail.sender.protocol=smtp
report.scheduler.mail.sender.port=587
report.scheduler.mail.smtp.starttls.enable=true
report.scheduler.mail.smtp.auth=true

You can find the locations here:

/opt/jasperreports-server-7.9.0/apache-tomcat/logs
/opt/jasperreports-server-7.9.0/apache-tomcat/webapps/jasperserver-pro/WEB-INF/logs