In CiviMail, the 'Count' of contacts are less thsan the group count - why?
Often a mailing is set up and the number of contacts is less than the total number of contacts in the group. This can be disconcerting if there is some doubt that the count is correct. So why is it different?
I can tell you that CiviMail will only count 'mailable' contacts, i.e. they have a valid email address and they are not opted out, on hold, marked 'do not email', or deceased. In database marketing parlance, these can be referred to as 'standard exclusions'.
So what are some best practice tips to be reassured about the numbers of contacts, keeping lists healthy and recommended workflow for regular monthly mailings?
Civi user guide is a good place to start https://docs.civicrm.org/user/en/latest/email/maintaining-healthy-email-lists/