unknown content-type encoding in mail handler causes infinite issue recreation

When an issue is received via email with an encoding JIRA doesn't recognise, it logs the following error:

2007-11-02 05:48:14,177 JiraQuartzScheduler_Worker-0 ERROR [service.util.handler.CreateIssueHandler] Could not create issue!
java.io.UnsupportedEncodingException: unicode-1-1-utf-7
at sun.io.Converters.getConverterClass(Converters.java:218)
at sun.io.Converters.newConverter(Converters.java:251)
at sun.io.ByteToCharConverter.getConverter(ByteToCharConverter.java:68)
at sun.nio.cs.StreamDecoder$ConverterSD.<init>(StreamDecoder.java:224)
at sun.nio.cs.StreamDecoder$ConverterSD.<init>(StreamDecoder.java:210)
at sun.nio.cs.StreamDecoder.forInputStreamReader(StreamDecoder.java:77)
at java.io.InputStreamReader.<init>(InputStreamReader.java:83)
at com.sun.mail.handlers.text_plain.getContent(text_plain.java:64)
at javax.activation.DataSourceDataContentHandler.getContent(DataHandler.java:745)
at javax.activation.DataHandler.getContent(DataHandler.java:501)
at javax.mail.internet.MimeBodyPart.getContent(MimeBodyPart.java:603)
at com.atlassian.jira.service.util.handler.AbstractMessageHandler.handleMultipart(AbstractMessageHandler.java:279)
at com.atlassian.jira.service.util.handler.AbstractMessageHandler.createAttachmentsForMessage(AbstractMessageHandler.java:234)

However, the issue is created, with an empty body, and the message is left at the IMAP server. The next time the email service runs, another empty issue is created. This continues forever until the mail is manually deleted from the server.

I have attached an example message that causes this issue.