Alert e-mails not always received properly

Dear all,

In the smart campaign that handles a filled in form and sends a confirmation e-mail to the lead, i've included an alert to me and my colleagues.

The purpose of this alert is ofcourse that we immediately know it when a new lead is created.

The only problem is, these alerts don't always arrive properly. I've constructed like this:

And in the 'To other e-mails' i've stated: me@example.com colleague1@example.com colleague2@example.com

We're eight in total and that this point three of us seem to receiving the e-mails, but the other five are going wrong.

Is there perhaps a different, better way to manage these alerts?

Thanks in advance!