Emails with Attachments Cause an Error in Mule

I have a working Mule 2.2.1 configuration with the imaps:connector. But I am not able to proceed emails with attachments. Any experience?

org.mule.api.service.ServiceException: Cannot route event as component "imap" is stopped. Component that caused exception is: SedaService{imap}. Message payload is of type: MimeMessage

Or alternatively type MimeBodyPart is reported instead of MimeMessage if I remove org.mule.transport.email.SimpleMailMessageAdapter.

I tried to restrict configuration as much as possible (no outbouds, no components), but it does not help.

    <imaps:connector name="imapConnector" checkFrequency="${imap.checkFrequency}" deleteReadMessages="${imap.deleteReadMessages}" >
        <imaps:tls-client path="${keystore}" storePassword="${keystore.password}" />
        <imaps:tls-trust-store path="${keystore}" storePassword="${keystore.password}" />
    </imaps:connector>

    <model>

        <service name="imap">
            <inbound>
                <imaps:inbound-endpoint host="${imap.host}"
                    port="${imap.port}" user="${imap.user}"
                    password="${imap.password}" connector-ref="imapConnector">

                </imaps:inbound-endpoint>
            </inbound>

        </service>

 开发者_StackOverflow中文版   </model>

Edit

Strange! Transformers do not help because they are not even called. I wrote a custom one doing nothing, just for debugging purpose. Transformer is called if is added to inbound. It causes skipping a component, even non existing.

I could not identify the problem because of FunctionalTestCase. Mule behaves differently there. The server throws understandable exception.

java.lang.ClassCastException: javax.mail.internet.MimeMultipart cannot be cast to java.lang.String
    at org.mule.transport.email.transformers.EmailMessageToString.doTransform(EmailMessageToString.java:57)

The default e-mail transformer EmailMessageToString does not expect that MimeMultipart may contain another MimeMultipart, not only string.