There could be many possible reasons that could lead to attachment issues in Outlook. This includes incorrect Outlook settings, file incompatibility, incorrect mail format, etc. Try resetting Outlook ...

When you send an email message from a Microsoft Outlook client that is configured incorrectly, the receiver may receive an attachment with the name winmail.dat. This is a binary attachment that ...

OK, I've had this happen twice. The last time I fixed it by removing the outlook profile, uninstalling outlook, deleting all files in \docs&settings\user\app_data\microsoft\outlook and then ...