It's most likely coming from a stack trace generated by your application. The JavaMail API is vulnerable to header injection via the Subject header, and you're probably seeing that phenomenon (though by accident).

For my own application, I wrote a subclass of SMTPAppender that truncates the Subject header at the first EOL character, which prevents this issue from occurring.


On Mon, May 13, 2013 at 8:20 PM, Jason Bennett <jasonab@acm.org> wrote:

I'm using Amazon SES with SSL to send emails via Logback's SMTPAppender. It usually works, but sometimes I receive the following error:

0:01:51,863 |-ERROR in ch.qos.logback.classic.net.SMTPAppender[EMAIL] - Error occurred while sending e-mail notification. com.sun.mail.smtp.SMTPSendFailedException: 554 Transaction failed: Illegal header 'Caused by'.

        at com.sun.mail.smtp.SMTPSendFailedException: 554 Transaction failed: Illegal header 'Caused by'.

        at      at com.sun.mail.smtp.SMTPTransport.issueSendCommand(SMTPTransport.java:2114)
        at      at com.sun.mail.smtp.SMTPTransport.finishData(SMTPTransport.java:1900)
        at      at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:1122)
        at      at javax.mail.Transport.send0(Transport.java:195)
        at      at javax.mail.Transport.send(Transport.java:124)
        at      at ch.qos.logback.core.net.SMTPAppenderBase.sendBuffer(SMTPAppenderBase.java:395)
        at      at ch.qos.logback.core.net.SMTPAppenderBase$SenderRunnable.run(SMTPAppenderBase.java:690)
        at      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1146)
        at      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at      at java.lang.Thread.run(Thread.java:679)


I'm aware that Amazon only allows emails with legal headers through SES, but I have no idea where Amazon is getting this header from. Has anyone else seen this?

jason


--
Jason Bennett, jasonab@acm.org
E pur si muove!
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