Checkmark changes to "X", radio buttons change to "Circle" when Acrobat Form is submitted via email.

I have an Acrobat order form that is completed digitally. After completion, the user signs the document and selects the security lock option. Finally, a submit block is submitted for the email transaction (transfer). When the email is opened by the recipient, the checkmarks are now "X's" and the radio button data is changed form a checkmark to a solid round circle. Why is this? Thank you.