Unable to import some exchange accounts

[mtanzer]

I have troubles to import some exchange accounts to Zimbra 5.0 - though I set ErrorTreshold to 0 the Migration Wizard stops at 483 of 660 Mails. On 20 other Accounts the Migration was working.

-2008 16:13:51 [3568]: (MI): Batch Adding Message d(Fri, 9 Nov 2007 09:24:02 -0000) fid(005)
21-02-2008 16:14:22 [3568]: Zimbra Exception: message not added, No upload token returned
21-02-2008 16:14:24 [3568]: (MI): Batch Adding Message d(Fri, 9 Nov 2007 09:25:06 -0000) fid(005)
21-02-2008 16:14:54 [3568]: Zimbra Exception: message not added, No upload token returned
21-02-2008 16:14:54 [3568]: (MI): Batch Adding Message d(Fri, 9 Nov 2007 09:29:47 -0000) fid(005)
21-02-2008 16:14:56 [3568]: (MI): Batch Added Message rid(0)
21-02-2008 16:14:56 [3568]: (MI): Executing batch request
21-02-2008 16:15:00 [3568]: (MI): Got response (3469 ms)
21-02-2008 16:15:00 [3568]: (MI): ERROR - error(s) detected in the server response
21-02-2008 16:15:00 [3568]: (MI): ERROR - The SOAP request  was logged to:  C:\DOKUME~1\BLAH~1.KOL\LOKALE~1\Temp\ZCSExchangeMigrationWizard-5.0.0_GA_1862\1-request.xml
21-02-2008 16:15:00 [3568]: (MI): ERROR - The SOAP response was logged to:  C:\DOKUME~1\BLAH~1.KOL\LOKALE~1\Temp\ZCSExchangeMigrationWizard-5.0.0_GA_1862\1-response.xml
21-02-2008 16:15:00 [3568]: (MI): Rid 0 failed: (service.FAILURE) (system failure: failed to analyze part)
21-02-2008 16:15:00 [3568]: (MI): The MAPI message was logged to C:\DOKUME~1\BLAH~1.KOL\LOKALE~1\Temp\ZCSExchangeMigrationWizard-5.0.0_GA_1862\1-000000009076054ca453f047883d6cde2c88155a07004ecc4c36ac7c444ca9a9f4255017f45d0000002abf1300004ecc4c36ac7c444ca9a9f4255017f45d0000002afaa40000.msg:
21-02-2008 16:15:00 [3568]: (MI): ERROR - The SOAP request  was logged to:  C:\DOKUME~1\BLAH~1.KOL\LOKALE~1\Temp\ZCSExchangeMigrationWizard-5.0.0_GA_1862\2-request.xml
21-02-2008 16:15:00 [3568]: (MI): ERROR - The SOAP response was logged to:  C:\DOKUME~1\BLAH~1.KOL\LOKALE~1\Temp\ZCSExchangeMigrationWizard-5.0.0_GA_1862\2-response.xml
21-02-2008 16:15:01 [3568]: (MI): Batch Adding Message d(Fri, 9 Nov 2007 09:30:04 -0000) fid(005)
21-02-2008 16:15:03 [3568]: (MI): Batch Added Message rid(0)
21-02-2008 16:15:03 [3568]: (MI): Executing batch request

Any Hints?