When you email native Excel files from SAS as an attachment using the EMAIL access method in a FILENAME statement, an error like the following might be generated when the files are opened: 

The error occurs when the mail server does not know which application to associate with the attachment.  These files might be created using the ODS destination for Excel or PROC EXPORT.  

If the Excel file has a .xlsx extension, the CONTENT_TYPE= option within the ATTACH= option might be needed in the FILENAME statement to associate the correct mime-type for the Office Open XML format (.xlsx).  Click the Full Code tab to see an example of applying the correct mime-type for the attachment.

Operating System and Release Information

ods excel file='c:\temp\test.xlsx'; 

proc print data=sashelp.cars; 
run; 

ods excel close; 

filename mailit email 
        to='joebloe@yahoo.com' 
        subject="ODS Excel Test" 
        attach=("c:\temp\test.xlsx" content_type="application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" lrecl=32000); 
run; 

data _null_; 
     file mailit; 
     put "ODS Excel Test"; 
run;