Same problem here after upgrading to 6.0.4.
For now, ask the sender to send the e-mail with the attachement as plain text.
How to change in outlook?
First make sure your global setting is set to use Plain Text or HTML:
1. In Outlook, select Tools > Options.
2. The Options dialog box appears. Select the Mail Format tab.
3. Under the Message Format heading, change Compose in this message format to Plain Text or HTML.
4. Click OK.
Next, make sure that the user who received the winmail.dat file is set for Plain Text or HTML messages:
1. If the user is in the Senderís contacts:
2. In Outlook, open the Contacts folder.
3. Open the record of the person who receives winmail.dat attachments.
4. Double click the receiver's email address.
5. The Email Properties dialog box will appear. Change Internet format to Let Outlook decide the best sending format. This will cause Outlook to use the global setting.
6. Click OK.
If the user is not in the Senderís contacts:
1. In Outlook, create a new message.
2. In the To field type in the email address of the user receiving the winmail.dat attachments, then hit the tab key. If Outlook doesnít automatically put a black underline under the name, click the Check Names button.
3. Double click the receiver's email address.
4. The Email Properties dialog box will appear. Change Internet format to Let Outlook decide the best sending format. This will cause Outlook to use the global setting.
5. Click OK.