ooO suddenly broken.

Last summer (during holiday) ooO was working, I can't remember that I've
changed anything, but ok ....

System Windows Server 2003 R2
Enterprise x64 Edition
SP2

Exchange Server 2007
Microsoft Corporation
Version: 08.00.0685.018

I checked already all aspects of ooO on this website regarding ooO:
http://www.msxfaq.de/konzepte/oof.htm.

I've searched web and MS Newgrops - I can't find a solution.

Settings

a)
[PS] Z:\>Get-RemoteDomain |fl

DomainName : *
CharacterSet : iso-8859-1
NonMimeCharacterSet : iso-8859-1
AllowedOOFType : ExternalLegacy
AutoReplyEnabled : True
AutoForwardEnabled : True
DeliveryReportEnabled : True
NDREnabled : True
MeetingForwardNotificationEnabled : False
ContentType : MimeHtmlText
DisplaySenderName : True
TNEFEnabled :
LineWrapSize : unlimited
MinAdminVersion :
AdminDisplayName :
ExchangeVersion : 0.1 (8.0.535.0)
Name : Standard
DistinguishedName : CN=Standard,CN=Internet Message
Formats,CN=
Global
Settings,CN=fsn-mettmann,CN=Microsof
t
Exchange,CN=Services,CN=Configuration,DC=
fsn-mettmann,DC=de
Identity : Standard
Guid : 57bf2f85-bd86-48e5-b18d-2e32b8c03631
ObjectCategory :
fsn-mettmann.de/Configuration/Schema/ms-Exc
h-Domain-Content-Config
ObjectClass : {top, msExchDomainContentConfig}
WhenChanged : 11.08.2010 18:10:48
WhenCreated : 12.05.2007 14:28:59
OriginatingServer : server.fsn-mettmann.de
IsValid : True


b)
set-mailbox <alias> ExternalOofOptions <InternalOnly | External>
both values checked - no change in behaviour

[PS] Z:\>set-mailbox "klaus deiss" -ExternalOofOptions external
[PS] Z:\>set-mailbox "klaus deiss" -ExternalOofOptions external
WARNING: Der Befehl wurde erfolgreich abgeschlossen, es wurden jedoch keine
Einstellungen von 'fsn-mettmann.de/Friedrichstrasse/Klaus Deiss' geändert.
[PS] Z:\>

c)
GDATA Outlook-Plugin deactivated