- Is this the default settings? If yes is there anyway we can disable it?
By default the HTML won't be attached to emails sent with blastula::attach_connect_email, but you can change this with the attach_output argument
- Sending email with attachment is good BUT is there any way that we can limit user so that the attachment is not being forwarded?
No, once an email is in an inbox, there is nothing Connect can do about how the contents are further distributed