Spring--cannot convert javax.mail.session

I am creating a mail session inside of my servlet context and then using JNDI to inject it into my spring framework design. Here's how the context looks:

<Resource name="mail/session" auth="Container"
            type="javax.mail.Session"
            mail.smtp.from="noreply@xxxx.com"
            mail.smtp.user="noreply@xxxx.com"
            mail.smtp.auth="true"
            mail.smtp.starttls.enable="true"
/>

And where I'm bringing it in:

  <bean id="smtpSession" class="org.springframework.jndi.JndiObjectFactoryBean">
    <property name="jndiName" value="java:comp/env/mail/session"/>
  </bean>

and where I'm injecting it into the spring java mail sender:

  <bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
      <property name="host" ref="smtpHost"/>
      <property name="password" ref="smtpPassword"/>
      <property name="port" ref="smtpPort"/>
      <property name="username" ref="smtpFrom"/>
      <property name="session" ref="smtpSession"/>
  </bean>

Now here's the message I'm getting:

Caused by: java.lang.IllegalStateException: Cannot convert value of type [javax.
mail.Session] to required type [javax.mail.Session] for property 'session': no m
atching editors or conversion strategy found
        at org.springframework.beans.TypeConverterDelegate.convertIfNecessary(Ty
peConverterDelegate.java:231)
        at org.springframework.beans.BeanWrapperImpl.convertIfNecessary(BeanWrap
perImpl.java:447)
        ... 51 more

Uh, what???? Why is it trying to convert it?