This question comes up frequently, so I thought it would be good to get a note out to everyone. In most schools, you cannot send an email to a student's "school" email address from outside the school's domain. Teachers and other students can email each other becuase they all have an account on the same closed system.
When adding new team members to your Windchill project, it is best to use the student's personal email address. An address that is not restricted by the school. I understand some students may not have an external email address. You'll need to work with those students and their parents to confirm their use of an external email address and discuss any restrictions applied to the account.
The Windchill invitations are sent from the Windchill server, using the email ID you used for your PTC account. If any of the recipients are blocking "unknown" email addresses, your message will be rejected or sent directly to the Spam folder.
If you can send a message to everyone from your own email account without any errors, there should be no reason why you cannot invite them to a Windchill project using the same email address.
