I cannot open word document attachments.

Why do I receive email attachments with .dat extension (which I cannot open)?

• I have a Windows PC. Yahoo is my ISP. The problem occurs (not often, but more frequently recently) when I open emails in Outlook (POP3). Sometimes the .dat attachments are meaningless (that is what a sender told me the first time I raised the issue). On the other hand, yesterday a client sent what he intended as a MS Word attachment, but it came through as .dat. (Workaround: He ended up copying the document text into the e-mail.) A few weeks ago, a sender included three attachments: One came through as MS Word, two as .dat. When I asked that the two be re-sent, the same problem occurred. The workaround was for the sender to convert them to PDF, which came through fine.

• Answer:

  The only files with a DAT extension will be WINMAIL.DAT, which was a dirty Microsoft hack used in older versions of Outlook to preserve rich text formatting.  Your sender needs to take action as prescribed in this Microsoft support document: http://support.microsoft.com/kb/278061. If that is not possible, a web based service exists to decode such files: http://www.winmaildat.com/ But you really need to ask the sender to make some changes or update to a more modern email program.