How to convert "Cross-forest mail contact" to "Mail Contact" in Exchange 2010?
Go to attribute editor, delete msExchRecipientTypeDetails and msExchOriginatingForest attributes. Then change msExchRecipientDisplayType to 6
Attributes before changes:
After editing we have only:
After such configuration Cross-forest mail contact will be shown in EMC as Mail Contact
Note: Don't think that it is best practice but as for me it works fine in test environment.