Use case: Use this procedure to configure message delivery restrictions for a user, group, or contact. Adjusting delivery restrictions helps control who can send messages, set size and recipient limits, and manage communication flow for security and compliance.
To configure message delivery restrictions, do the following:
- Open User, Group, or Contact properties, select the Mailbox tab, and click Delivery Restrictions.
- Configure Accept messages to allow messages from a limited list of users and reject all others.
- To reject emails from external (non-authenticated) users, select Require that all senders are authenticated.
- Configure Reject messages to block messages from a limited list of users and allow all others.
- Configure Maximum recipients for sent messages to limit the number of recipients the user can send to.
- Configure Maximum size for sent messages to restrict the size of emails the user can send.
- Configure Maximum size for received messages to restrict the size of emails the user can receive.
- Click OK twice to apply the settings.
Note:
- For hybrid contacts and hybrid groups, Accept and Reject recipients are selected from the on-premises Active Directory.
- Recipients must have a valid email alias and address to be used in Accept and Reject restrictions.
- For all other mail objects, Accept and Reject recipients are selected from Exchange Online.
ID:KB_017_How-To-Configure-Message-Delivery-Restrictions
