submit a form button not working with Outlook

I have several forms I use to gather information from clients.  Each has a submit form button that up until today sent the entire pdf to me by email.  Now, when I s=click on the submit button I get this error message:

An error occurred while trying to create a mail document.  Acrobat is unable to complete your request. If you are not sure how to proceed further, you can save your form and return it manually using your Internet email service.

What has changed?