how to stop winmail.dat files being sent?

[Fiona&Geoff]

I am running Windows 10, Office 2007 and Adobe Acrobat X Pro. I am trying to send individually numbered pdf attachments to around 200 people on my distribution list using Outlook. I can send the emails but some recipients aren't getting my pdf file but instead a winmail.dat which they cannot open. Is there a way round this or can anyone suggest an alternative solution? I have tried changing the mail option in outlook to HTML or plain text format as opposed to rich text.

[J B]

Just to clear things up you are using 'Office Outlook' e mail program as opposed to Outlook the new word for Hotmail - good old Microsoft to change that name just to make it easier for us all.

I guess you open a new message and attach the pdf and press send?

If there are problems, is there an option in Acrobat to 'send to' 'mail recipient'?

Just clutching at straws really as I use Thunderbird for my e mail and Foxit for my pdf stuff