(Please, look at attached document)

We have sent our customers invoices with this procedure:
(From list view)
- Select invoices to send.
- Action "Send & Print"
Everything is recorded in Chatter, but the "envelope" does not appear. We see that it does not track recipients. The type / subtype of the recorded message are: Email / blank. 

However, if you use the "Send & Print" button from the invoice form, the envelope appears and the recipients are tracked. The type / subtype of the recorded message are: Comment / discussions. 

Why is that? We want to check if there is any error in batch sending of invoices.

https://www.dropbox.com/s/chci0nszrys3lhv/Not Tracking Recipients.docx?dl=0