Hostname vs Realm in XMPP

[Paul]

Hello, I have a question about realm vs hostname in xmpp

My jabber id is paul at domain.com for example.My SRV says that the jabber 
server for this is at jabber.domain.com

Pidgin passes the hostname rather than the domain name as the realm - so 
passes jabber.domain.com to my jabber server (I am decoding the base64 
in the debug log).  The jabber server then rejects the authentication as 
being an unauthorised host.   This is with or without a connect server 
defined in advanced.

I am wondering why pidgin doesn't pass the domain name as the realm, or 
how I can otherwise get this to work.Xabber and Kopete both seem to 
treat the domain name as the realm.

I doubt I am the only one where the domain name doesn't match the 
hostname exactly, so I must have something not configured right.  The 
backend is an ejabberd server.

Any ideas?

Paul