C0070005 error adding aSMTP address from child domain

[Georgestark]

Guys,
I need a child domain hosted in a different country to be able to add or
edit SMTP addresses for the child doman users.
We have a single exchange organisation hosted in the UK.
We have a vpn link between the child domain and our head office
The head office hosted the forest DC and the first exchange server, we have
other exhcange servers accross the UK.

I have given the Child domain Admin local admin rights to the exhange server.

when the child domain admin tries to edit or had add SMTP address somtimes
it works somtimes it does not.
Error: Access denied, win32, c0070005
http://support.microsoft.com/?kbid=905809 has been tried (Child domain
admins member of exchange Local admins)

I know the issue is that the ADUC is trying to connect to an exchnage server
to determine if the SMTP address exists and then add or modify.
The child domain cannot see all exchange servers, I have tried adding the
Prefered Server reg key but this does not work (parameter key does not exist).

I need to fix the exchange server the child domain server uses to do the
LDAP look up.

[Georgestark]

My God this is the second post I have had no replies on What is going on this
used to be so good, Am I trying to get a fix on somthing above everybodies
understanding.

George