Question : Winmail.dat issues Exchange 2010 Server

We have installed a new Exchange Server. Prior the that the client was sending via ISP's SMTP server. They assure me there were no issues with the old set-up.
The customer sends a lot of PDF attachments. Some, but not all, of the recipients, are getting winmail.dat attachments at the other end, rather than the PDF. Apparently users with problems are recieving are on PCs and Macs & the same issue arriving at BlackBerrys.
They have a mixture of Outlook 2003 and Outlook 2007. It's happening when they use either mail program to send the e-mail and attachment.
It happens when the mail format is set to "Plain Text", too.
I am unable to re-create, unfortunately, since it comes through to me fine on Outlook 2007; also we have tested to Gmail account and it's fine and also to a test POP3 account with Eudora collecting mail and it's fine.
We are trying to find out more details as to the systems at the other end which are having problems, but (see above) apparently it's PCs, Macs & BlackBerrys.
Any assistance would be appreciated as this is causing real issues.
Thanks in advance.

Answer : Winmail.dat issues Exchange 2010 Server

Touch wood, this seems to have sorted the issue.

For the record, full details as follows:-
Exchange 2010 Management Console
Organization Configuration > Hub Transport.
In the work pane, select the Remote Domains tab on the right, and then double-click the remote domain you want to configure (in this case *)
Under "Message Format", "Exchange rich-text format:" from "Determined by individual users settings" to "Never use".