The most common reason that an email does not have any recipients is that you are sending an email to households and the household does not have Send Mail checked.  The other possibility is that the record does not have any email addresses or any valid email addresses.  Note: A list of all invalid email addresses can be accessed by navigating to Security > Maintenance > Validate Emails.  You need the Security Full role to access this page.

See also
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PCR Educator K-12 School Information System is an online database engineered for independent and private schools to deliver the highest level of flexibility, unique experience, transparent communication and customized design. Being a complete cloud-based solution, PCR Educator system guarantees convenient access anytime, anywhere.