[rt-users] External users unable to create tickets since ExternalAuth activated

[Nicôle Layne-Balram]

Since implementing external auth (LDAP option), RT works as expected for users within AD, but I've just realized that external users are unable to create tickets, even with the appropriate "Everybody" permissions set via the web interface (globally as well as queue-specific).

Error within logs: 
*timestamp* RT RT: RT::Authen::ExternalAuth::CanonicalizeUserInfo returning Comments: Autocreated on ticket submission, Disabled: 0, EmailAddress: yyy at hotmail.com, Name: yyy at hotmail.com, Password: , Privileged: 0, RealName: Jane Doe (/opt/rt3/local/plugins/RT-Authen-ExternalAuth/lib/RT/Authen/ExternalAuth.pm:536) 
Jan 10 21:21:58 RT RT: Couldn't load user 'yyy at hotmail.com'.giving up (/opt/rt3/bin/../lib/RT/Interface/Email.pm:947)

RT_SiteConfig.pm:
Set($rtname , "xxx.com");
Set($Organization , "xxx.com");
Set($Timezone , 'US/Eastern');
Set($DatabaseType , 'mysql');
Set($DatabaseHost   , 'localhost');
Set($DatabaseRTHost , 'localhost');
Set($DatabasePort , '');
Set($DatabaseUser , 'rt');
Set($DatabasePassword , 'xyz');
Set($OwnerEmail , 'root');
Set($RTAddressRegexp , '([a-z]+)\@rt\.xxx\.com$');
Set($ValidateUserEmailAddresses, 1);
Set($CorrespondAddress , 'no-reply at rt.xxx.com');
Set($CommentAddress , 'no-reply-comment at rt.xxx.com');
Set( $WebDomain, 'rt.xxx.com' );
Set($WebPath, "");
Set($CanonicalizeRedirectURLs, 1);
Set($LogToSyslog , 'info');
Set($UnsafeEmailCommands,1);
Set($LogToSyslog, "debug");
Set($AutoCreateNonExternalUsers, 1);
Set($AutoCreate, {Privileged => 1});
Set(@Plugins,qw(RT::FM RT::Extension::QueueDeactivatedScrips RT::Extension::MobileUI RT::Authen::ExternalAuth));
require "/opt/rt3/local/plugins/RT-Authen-ExternalAuth/etc/My_RT_SiteConfig.pm";

1;

External User gets two returned e-mails from no-reply at rt.xxx.com:
RT could not load a valid user, and RT's configuration does not allow for the creation of a new user for your email.
User 'yyy at hotmail.com' could not be loaded in the mail gateway

Any help and suggestions would be greatly appreciated.

Thanks,
Nicôle