Workaround 1
Run "Outlook.exe /CleanAutoCompleteCache" to clear the cache.
Workaround 2
Add the problematic LEDN to the contact as an additional x500 address.
The value can be derived from the NDR message. For example:
IMCEAEX-_O=Organization_OU=Exchange+20Administrative+20Group_cn=Recipients_cn=user@company.com
Would translate to:
/o=Organization/OU=Exchange Administrative Group/cn=Recipients/cn=user
For more information, also see http://support.microsoft.com/kb/2807779.
Workaround 3
For additional information see http://support.microsoft.com/kb/2682333