We are using following:
Outlook Configured as email Client
Our General Manager and a staff from Sales department has enabled Tracking feature of CRM for all emails and when they are using CRM, just after that config some outgoing emails are arrive to target user's inbox with winmail.dat attachments.
For example, when they send Outlook 2007 Excel attachments with *.xlsx extension, receiver will see resulting file with winmail.dat extension.
So what should we check first?