2008-07-15 07:31:41 1KIiku-0005is-DZ == example@example.com R=temp_defer defer (-1): Mail Server Upgrade in Progress.  Message Queued.

This error may appear after upcp on cPanel powered server. It is quite simple to fix it:

#rm /usr/local/cpanel/etc/exim/cf/fail_remote_domains -f

#/scripts/buildeximconf

#/scripts/restartsrv_exim

As you probably understand the above will overwrite any Exim customizations you might have had