Microsoft has officially unblocked the University. You should be able to send to any of the below email addresses. Thank you for your patience.
...
Members of our community with @fairfield.edu email accounts are currently unable to email addresses provided by Microsoft. These email addresses include:
This is due to many members of our community following malicious links in phishing emails last week which resulted in their email accounts becoming part of the phishing scam – Microsoft blocked our domain because of this.
...