Mail to RT Fails - RT::User::LoadByName Unimplemented

Team,

One of my users is getting the following error when replying to tickets
using his email client. The error he is getting is below:

Can anyone tell me what RT::User::LoadByName Unimplemented means and how
I can fix this?

Thanks

-Stevo

From - Mon Jul 31 12:14:14 2006
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FILETIME=[7DA8B540:01C6B4D5]

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

pipe to |/usr/local/rt3/bin/rt-mailgate --queue IT_Support --action
correspond --url http://itsupport.xxx.local/
generated by itsupport@itsupport.xxx.local
local delivery failed

The following text was generated during the delivery attempt:

------ pipe to |/usr/local/rt3/bin/rt-mailgate --queue IT_Support
–action correspond --url http://itsupport.xxx.local/
generated by itsupport@itsupport.xxx.local ------

RT server error.

The RT server which handled your email did not behave as expected. It
said:

RT::User::LoadByName Unimplemented in RT::Interface::Email.
(/usr/local/rt3/local/lib/RT/Interface/Email_Local.pm line 54)

Stack:
[/usr/local/lib/perl5/site_perl/5.8.7/DBIx/SearchBuilder/Record.pm:496]
[/usr/local/rt3/local/lib/RT/Interface/Email_Local.pm:54]
[/usr/local/rt3/local/lib/RT/Interface/Email/Auth/MailFrom_Local.pm:125]
[/usr/local/rt3/lib/RT/Interface/Email.pm:605]
[/usr/local/rt3/share/html/REST/1.0/NoAuth/mail-gateway:58]