I have 60 profiles I am trying to send to. They have not been unsubscribed as they've never been sent anything before. They are all activated and confirmed accounts. When I create a campaign, I choose to send after I test but it is stating that it will only send to 41 profiles.
I had a similar problem, mass mail was not sending to all users of the selected segment.
There were no problems on the accounts.
After some research the limitation was found at SMTP provider -mailjet-,.
When a user selects spam or there is a hard bounce from the users email address, their system blocks that email and do not deliver any more mails.
May be your problem could be something like this?