Microsoft Outlook's MSG and EML files can only be printed to your system Default printer, despite the selected printer mapped in the Print Queue Mapping tab. When you right-click on a document listed in a Document Search Results window and select Print Selected or Print All, the document gets printed directly to the default printer. This is a limitation of Microsoft Outlook.
Note:
The only way to print to a different printer is to open the message for display in Microsoft Outlook's default viewer and select the Print function from there. From within Microsoft Outlook's Print dialog, you may select a printer different from your DMS default printer.