Notification Activity - Emailing attachments

[dscon9128]

Hello,

I had a question regarding the type of file attachment you could email out with the Notification activity. I have created a .dat file which is very small in size, but DS does NOT include the file as an attachment and throws a message sayin "WARNING - MISSING ATTACHMENT: Cannot open attachment file '*/ComparesReport.dat ' ".
However, when i try using a .txt format, it works just fine. Nothing changed between scenario1 and scenario2, with the exception of the file extension.

So are there certain types of file formats which DS wont pick up?

All you help is greatly appreciated.

Thanks!