[Update]

The problem with the certificates is solved:

i'v reinstalled them, like rob1n said and installed again the ones from our ext. CA and the exchange-Server, then i am able to go one step more in the MfE-setup-process:
I can choose now, what i want to synchronize and proceed by clicking next, but the synchronisationprocess stops imediately, because i get an Exchange deny-Error. In the N900-syslog i can see the this:

Feb 8 23:59:26 Nokia-N900-51-1 ke_recv[7783]: prop_modified:1889: udi /org/freedesktop/Hal/devices/platform_slide modified button.state.value
Feb 8 23:59:49 Nokia-N900-51-1 ke_recv[7783]: session_sig_handler:860: NotificationClosed for 1
Feb 8 23:59:49 Nokia-N900-51-1 ke_recv[7783]: notification_closed:814: unknown dialog id: 1
Feb 8 23:59:55 Nokia-N900-51-1 activesync[7930]: AS-COMMON-UTILS Version: libas-common-utils (0.0.2-27+0m5) unstable; urgency=low
Feb 8 23:59:55 Nokia-N900-51-1 activesync[7930]: SyncScheduler: Cancel all actions
Feb 8 23:59:56 Nokia-N900-51-1 activesync[7930]: AS-LIB: Version: libas-protocol (0.0.2-27+0m5) unstable; urgency=low
Feb 8 23:59:56 Nokia-N900-51-1 activesync[7930]: AS-LIB: Created factory for version 2.5
Feb 8 23:59:57 Nokia-N900-51-1 activesync[7930]: HTTP STATUS: 403
Feb 8 23:59:57 Nokia-N900-51-1 activesync[7930]: AS-LIB: FolderSync failed with status 403. Abort retrieving estimations
Feb 8 23:59:57 Nokia-N900-51-1 activesync[7930]: ActionFullSync: ItemEstimate failed with status 403. Abort.
Feb 8 23:59:57 Nokia-N900-51-1 [7902]: GLIB DEBUG hildon-1 - ca_context_play_full Success
Feb 9 00:00:00 Nokia-N900-51-1 ke_recv[7783]: session_sig_handler:860: NotificationClosed for 6
Feb 9 00:00:00 Nokia-N900-51-1 ke_recv[7783]: notification_closed:814: unknown dialog id: 6
Feb 9 00:01:45 Nokia-N900-51-1 [7902]: GLIB DEBUG hildon-1 - ca_context_play_full Success


and on the apache-reverse-proxy side in front of the exchange-server i get this:

N900 (IP, Name and IMEI replaced with [...]):
access.log.1:[IP] - - [08/Feb/2010:16:40:10 +0100] "OPTIONS /Microsoft-Server-ActiveSync HTTP/1.1" 200 - "-" "N900/
1.1"
access.log.1:[IP] - - [08/Feb/2010:16:40:11 +0100] "POST /Microsoft-Server-ActiveSync?Cmd=FolderSync&DeviceId=[My IMEI]&DeviceType=SmartPhone HTTP/1.1" 403 44 "-" "N900/1.1"


Why do i see a http error, i thought MfE handles with https?

Au contrair, same MfE with an I-Phone works like a charme (IP, Name and IMEI replaced with [...]):

access.log.1:[IP] - - [08/Feb/2010:13:32:50 +0100] "POST /Microsoft-Server-ActiveSync?User=[my login]&DeviceId=Appl889420HR3NR&DeviceType=iPhone&Cmd=Fo lderSync HTTP/1.1" 449 74 "-" "Apple-iPhone/704.11"
access.log.1:[IP] - - [08/Feb/2010:13:32:51 +0100] "POST /Microsoft-Server-ActiveSync?User=[my login]&DeviceId=Appl889420HR3NR&DeviceType=iPhone&Cmd=Pr ovision HTTP/1.1" 200 945 "-" "Apple-iPhone/704.11"
access.log.1:[IP] - - [08/Feb/2010:13:32:51 +0100] "POST /Microsoft-Server-ActiveSync?User=[my login]&DeviceId=Appl889420HR3NR&DeviceType=iPhone&Cmd=Pr ovision HTTP/1.1" 200 54 "-" "Apple-iPhone/704.11"
access.log.1:[IP] - - [08/Feb/2010:13:32:51 +0100] "POST /Microsoft-Server-ActiveSync?User=[my login]&DeviceId=Appl889420HR3NR&DeviceType=iPhone&Cmd=Fo lderSync HTTP/1.1" 200 1116 "-" "Apple-iPhone/704.11"
access.log.1:[IP] - - [08/Feb/2010:13:32:53 +0100] "POST /Microsoft-Server-ActiveSync?User=[my login]&DeviceId=Appl889420HR3NR&DeviceType=iPhone&Cmd=Sy nc HTTP/1.1" 200 111 "-" "Apple-iPhone/704.11"
access.log.1:[IP] - - [08/Feb/2010:13:32:53 +0100] "POST /Microsoft-Server-ActiveSync?User=[my login]&DeviceId=Appl889420HR3NR&DeviceType=iPhone&Cmd=Sy nc HTTP/1.1" 200 2209 "-" "Apple-iPhone/704.11"
access.log.1:[IP] - - [08/Feb/2010:13:32:54 +0100] "POST /Microsoft-Server-ActiveSync?User=[my login]&DeviceId=Appl889420HR3NR&DeviceType=iPhone&Cmd=Sy nc HTTP/1.1" 200 1668 "-" "Apple-iPhone/704.11"


Funny thing, isn it?

Does anyone know, why my login and foldersync reach an error?
The commands that are shown in the apache-log doesn't seems equal in the syntax used.

with regards,
Christian