[Exim] Mail server connected via PPP ...

Hello exim users, I work in an ISP and have a problem with some customer's
mail servers connected via PPP. My linux box running exim 3.03 is the secondary MX for these customer's domains and is supposed to defer and maintain in queue incoming messages for these domains when their mail servers are not using their PPP connection. These are some of the errors extracted from the exim mainlog file concerning incoming messages for one of these servers:

1999-11-16 18:34:50 11nrBL-0004Fg-00 ** gcasado@??? R=lookuphost2 T=remote_smtp2: retry time not reached for any host after a long failure period

1999-11-15 09:07:31 11nLpz-0007or-00 == aaellos@??? T=remote_smtp2
defer (113): No route to host
1999-11-15 09:07:31 11nLpz-0007or-00 ** aaellos@???: retry timeout
exceeded

As you can see for these two differents incoming messages they are inmediately rejected and not deferred for later delivery. You can also see that I'm using a different Router and delivery transport for this domain (like for the other domains with the same problem) , they are: R=lookuphost2 and T=remote_smtp2 .

These are the corresponding entries in configure file:

FOR TRANSPORTS

remote_smtp:
driver = smtp

remote_smtp2:
driver = smtp
retry_include_ip_address = false


FOR ROUTERS

lookuphost:
driver = lookuphost
transport = remote_smtp

lookuphost2:
driver = lookuphost
transport = remote_smtp2
domains = rendivalores.com:agemar.com.ve:avilaquimica.com

The strangest fact in this stuff is that I have been alternating these "problematic" domains from one router to the other each time these errors come back to surface but I cannot predict when this is going to happen, this is why I'm asking for your help ...

Thanks in advance...

Leonardo Fernandez.