Mail is sending text attachments rather than including the text inline
I was facing the same problem and figured out what was going wrong.

In mail, when you copy or drag the attachment, all text below attachment is treated as attachment hence it converts it to attachment and no text goes to the recipient.

All you need to do is in menu bar Edit &gt; Attachment &gt; Always insert attachment at end of message.

This will now always copy your attachments to the end and your text will remain safe in email.