In emails sent to a group of people, MailTrack isn’t able to identify the individuals that have opened the email or not.
The reason is that tracking multiple people in a single email affects the deliverability of your emails, for example, your messages could be classified as Spam or send to Promotions tab. The result is that your emails will be less opened.
Technically speaking, group email tracking requires to set up your own email servers, you can't use Gmail (Google) servers anymore, but your own emails servers will never be as reliable that Gmail (Google) ones.
We are sorry about that, but for those reasons we prefer not to offer a service that is not reliable enough and will affect the deliverability of your emails.
The easiest work around to this limitation is to send separate emails to each person. Response and open rates of group emails are lower than emails to single individuals, so our recommendation is to avoid them.
Group emails make mostly sense emails send internally inside a company, but in that case, you can ask your colleagues to install Mailtrack, only in that case Mailtrack will provide you reliable tracking for group emails.