Is there any injection vulnerability in the body of an email?

Question

AFAIK there is only a vulnerability within the HEADERS of an email when using user data correct?

I am using the below function to sanitize my data, however I have so

Answer 1

You can also inject MIME boundary into multipart messages, if the boundary is not randomized. That way you can inject arbitrary content (e.g. attachements with malware).

Example (not directly email-related but still): https://bugzilla.mozilla.org/show_bug.cgi?id=600464