After upgrading to version 4.5, the boss can no longer send email to Outlook 2003 distribution lists. She's getting the following error:

Code:
Note: Soap Fault. Please recreate and resend the message. Details below:

Error Code: mail.SEND_ABORTED_ADDRESS_FAILURE 
Error Text: Invalid address: <"Staff">
The logs show the following:

Code:
2007-02-26 09:36:48,761 WARN  [http-81-Processor98] [mid=20;ip=x.x.x.x;name=xxx@xxx.xxx;] MailSender - exception ocurred during SendMsg
javax.mail.SendFailedException: Invalid Addresses;
  nested exception is:
        class com.sun.mail.smtp.SMTPAddressFailedException: 504 <Staff>: Recipient address rejected: need fully-qualified address

        at com.sun.mail.smtp.SMTPTransport.rcptTo(SMTPTransport.java:1141)
        at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:536)
        at javax.mail.Transport.send0(Transport.java:151)
        at javax.mail.Transport.send(Transport.java:80)
        at com.zimbra.cs.mailbox.MailSender.sendMessage(MailSender.java:368)
        at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(MailSender.java:248)
        at com.zimbra.cs.operation.SendMsgOperation.callback(SendMsgOperation.java:110)
        at com.zimbra.cs.operation.Operation.schedule(Operation.java:190)
        at com.zimbra.cs.service.mail.SendMsg.handle(SendMsg.java:140)
        at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEngine.java:262)
        at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:162)
        at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:84)
        at com.zimbra.soap.SoapServlet.doPost(SoapServlet.java:223)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
        at com.zimbra.cs.servlet.ZimbraServlet.service(ZimbraServlet.java:162)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:541)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:667)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
        at java.lang.Thread.run(Thread.java:613)
2007-02-26 09:36:48,761 INFO  [http-81-Processor98] [mid=20;ip=10.1.1.90;name=wynne_smith@bmwcca.org;] SoapEngine - handler exception
com.zimbra.cs.mailbox.MailServiceException: Invalid address: <"Staff">
        at com.zimbra.cs.mailbox.MailServiceException.internal_SEND_FAILURE(MailServiceException.java:375)
        at com.zimbra.cs.mailbox.MailServiceException.SEND_ABORTED_ADDRESS_FAILURE(MailServiceException.java:379)
        at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(MailSender.java:298)
        at com.zimbra.cs.operation.SendMsgOperation.callback(SendMsgOperation.java:110)
        at com.zimbra.cs.operation.Operation.schedule(Operation.java:190)
        at com.zimbra.cs.service.mail.SendMsg.handle(SendMsg.java:140)
        at com.zimbra.soap.SoapEngine.dispatchRequest(SoapEngine.java:262)
        at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:162)
        at com.zimbra.soap.SoapEngine.dispatch(SoapEngine.java:84)
        at com.zimbra.soap.SoapServlet.doPost(SoapServlet.java:223)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:709)
        at com.zimbra.cs.servlet.ZimbraServlet.service(ZimbraServlet.java:162)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
        at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:541)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:667)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
        at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
        at java.lang.Thread.run(Thread.java:613)
Caused by: javax.mail.SendFailedException: Invalid Addresses;
  nested exception is:
        class com.sun.mail.smtp.SMTPAddressFailedException: 504 <Staff>: Recipient address rejected: need fully-qualified address

        at com.sun.mail.smtp.SMTPTransport.rcptTo(SMTPTransport.java:1141)
        at com.sun.mail.smtp.SMTPTransport.sendMessage(SMTPTransport.java:536)
        at javax.mail.Transport.send0(Transport.java:151)
        at javax.mail.Transport.send(Transport.java:80)
        at com.zimbra.cs.mailbox.MailSender.sendMessage(MailSender.java:368)
        at com.zimbra.cs.mailbox.MailSender.sendMimeMessage(MailSender.java:248)
        ... 25 more
This distribution list worked in version 4.0x, but now it's making her angry and putting me in some serious hot water.

She's using Outlook 2003 with the latest version of the Outlook Connector installed. She categorically refuses to use a different email client (including the web client), so I need to find a way to appease her.

Any ideas?

Thanks

Edit: forgot to mention this is version 4.5 Network Edition running on Mac OS X 10.4.9