Mule downloads e-mail body as well as attachment - mule

Question

How can I get Mule to download just attachments using pop3? I tried following the example at http://www.mulesoft.org/documentation/display/current/POP3+Transport+Reference as closely as possible, but I keep getting two files: one with the e-mail body and one with the actual attachment. Here's the flow I'm using:
<pop3:connector name="pop3Connector" checkFrequency="5000" doc:name="POP3"/>
<expression-transformer name="returnAttachments" doc:name="Expression">
<return-argument evaluator="attachments-list" expression="*" />
</expression-transformer>
<file:connector name="fileName" doc:name="File">
<file:expression-filename-parser/>
</file:connector>
<flow name="incoming-orders" doc:name="incoming-orders">
<pop3s:inbound-endpoint host="pop.gmail.com" port="995" user="myuser%40mydomain" password="mypassword" responseTimeout="10000" doc:name="POP3" transformer-refs="returnAttachments" />
<collection-splitter doc:name="Collection Splitter"/>
<file:outbound-endpoint path="C:/popthreetest" outputPattern="#[function:datestamp].dat" doc:name="File">
<expression-transformer>
<return-argument expression="payload.inputStream" evaluator="groovy" />
</expression-transformer>
</file:outbound-endpoint>
</flow>
Thanks!
edit:
Here's the final flow based on #David Dossot's answer. I have an added complexity in that I'm reading in a JSON file that specifies attachment names and an arbitrary destinations for the attachment. I included the replaceAll because I was getting an error about an invalid character in the path file:///C:\.
<pop3:connector name="pop3Connector" checkFrequency="5000" doc:name="POP3"/>
<expression-transformer name="returnAttachments" doc:name="Expression">
<return-argument evaluator="attachments-list" expression="*" />
</expression-transformer>
<file:connector name="DestinationsFileConnector" doc:name="File" autoDelete="false" streaming="true" validateConnections="true">
<file:expression-filename-parser/>
</file:connector>
<file:endpoint path="C:/popthreetest/" name="DestinationsFileEndpoint" responseTimeout="10000" doc:name="File" connector-ref="DestinationsFileConnector">
<file:filename-regex-filter pattern="destinations\.json" caseSensitive="true"/>
</file:endpoint>
<mulerequester:config name="DestinationsMuleRequestorConnector" doc:name="Mule Requester"/>
<flow name="incoming-orders" doc:name="incoming-orders">
<pop3s:inbound-endpoint host="pop.gmail.com" port="995" user="myusername%40mydomain" password="mypassword" responseTimeout="10000" doc:name="POP3" transformer-refs="returnAttachments" />
<collection-splitter doc:name="Collection Splitter"/>
<set-variable variableName="MessagePart" value="#[message.payload]" doc:name="MessagePart"/>
<logger message="Got #[message.payload.dataSource.name]." level="INFO" doc:name="Logger"/>
<mulerequester:request config-ref="DestinationsMuleRequestorConnector" resource="DestinationsFileEndpoint" doc:name="GetDestinations"/>
<json:json-to-object-transformer returnClass="java.util.HashMap" doc:name="JSON to Object"/>
<choice doc:name="Choice">
<when expression="#[message.payload.get(MessagePart.dataSource.name) != null]">
<set-payload value="#[message.payload.get(MessagePart.dataSource.name)]" doc:name="Destination List"/>
<foreach doc:name="For Each">
<logger message="Saving to #[message.payload]." level="INFO" doc:name="Logger"/>
<set-variable variableName="DestinationPath" value="#[java.nio.file.Paths.get(message.payload).getParent().toString().replaceAll('\\\\', '/')]" doc:name="DestinationPath"/>
<set-variable variableName="DestinationPattern" value="#[java.nio.file.Paths.get(message.payload).getFileName()]" doc:name="DestinationPattern"/>
<logger message="Saving to #[DestinationPattern] in #[DestinationPath]." level="INFO" doc:name="Logger"/>
<set-payload value="#[MessagePart]" doc:name="MessagePart"/>
<file:outbound-endpoint path="#[DestinationPath]" outputPattern="#[DestinationPattern]" doc:name="File">
<expression-transformer>
<return-argument expression="payload.inputStream" evaluator="groovy"/>
</expression-transformer>
</file:outbound-endpoint>
</foreach>
</when>
<otherwise>
<logger message="Did not find destination(s) for #[MessagePart.dataSource.name]." level="INFO" doc:name="Logger"/>
</otherwise>
</choice>
</flow>
For completeness, here's the JSON file:
{
"attachment-name.txt": [
"C:/popthreetest/firstDestination.txt"
, "C:/path/to/secondDestination.txt"
, "C:\\popthreetest\\destination\\using-backslashes.txt"
]
}

Answer 1

An email with attachment is a multi-part email into which attachments are parts but also the body. Hence Mule can only download "the whole package" and give the different parts to you.
You should be able to filter the body part after the collection-splitter based on the name of the part.
Alternatively, you could use a MEL expression to drop the first element of the collection, which is typically the body (Mule uses this technique internally to set the message payload: https://github.com/mulesoft/mule/blob/mule-3.x/transports/email/src/main/java/org/mule/transport/email/transformers/EmailMessageToString.java#L50 )