Email recipients cannot read PDF files I send from Outlook

I have been sending emails with PDF attachments to a contact (they are using Lotus notes).  When I send these emails from my Outlook 2007 email client with the attached PDFs the recipient cannot read the PDF files.  When I send the same PDF attachments to this contact, they can read the PDF files.  I do not understand what could be causing this.  All my other contacts can read my PDF attachments.  My contact says that they can read other peoples (not from my company) PDF attachments.

I looked online and one suggestion was that I use plain text format for my outgoing emails.  This did not help my situation.

Does anyone have any good suggestions for me?
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Joe Winograd, Fellow&MVEDeveloperCommented:
Are the attachments being received as <winmail.dat> files? If so, these two threads may help:

Regards, Joe

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