I have an application that I'm currently testing with the SMTPAppender. The application currently has test logic like the following...

def main(args: Array[String]) {
<configure logging>
error("Error 1", new IOException("IOE 1"))
error("Error 2", new IOException("IOE 2"))
error("Error 3", new IOException("IOE 3"))
error("Error 4", new IOException("IOE 4"))
<run forever>
}

When disabling asynchronousSending, all is fine. When enabling asynchronousSending, I'm only receiving 1 e-mail from the 4 error messages. The 1 e-mail that I get has a mix of errors from the 4 errors in the snippit above.

I get an email with the subject "Error 1" but in the body, it says "Error 4".

e.g.
Subject:
ERROR - Tonys-MacBook-Pro.local - c.server.App$ - Error 4

Body:
2014-04-14 16:49:55,592 ERROR com.server.App$ - Error 1
java.io.IOException: IOE 1
at com.server.App$.main(App.scala:33)
at com.server.App.main(App.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

Here's my config:

<appender name="EMAILER" class="ch.qos.logback.classic.net.SMTPAppender">
<smtpHost>smtp.xx.net</smtpHost>
<smtpPort>587</smtpPort>
<STARTTLS>true</STARTTLS>
<username>xx@xx.com</username>
<password>xx</password>

<to>xx@xx.com</to>
<from>xx@xx.com</from>
<asynchronousSending>false</asynchronousSending>
<includeCallerData>true</includeCallerData>

<subject>ERROR - ${HOSTNAME} - %logger

- %message</subject>
<layout class="ch.qos.logback.classic.PatternLayout">
<pattern>%date %-5level %logger - %message%n%ex</pattern>
</layout>

<!-- Only accept logs of ERROR or higher -->
<filter class="ch.qos.logback.classic.filter.ThresholdFilter">
<level>ERROR</level>
</filter>
</appender>