Help with text attachments

I really need to force plain text attachments to be added to emails as
attachments and not inline. I’ve found a few places in the code that
seemed like they’d be helpful, but I have not been able to find where
the document actually gets added to the email. If I have to live with
all plain text files being treated this way, that’s fine. I’m emailing
essentially pem format ssl certificates as text files with specific file
names and some email clients don’t display the file name or they
reformat the file, breaking the file integrity. We’ve been sending the
attachments separately, outside of RT, which kneecaps us a bit later.