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! Get Firefox! - http://getfirefox.com