1. In the EAC, navigate to Recipients > Mailboxes.
   
   
2. In the list of user mailboxes, click the mailbox that you want to configure message delivery restrictions for, and then click Edit .
   
   
3. On the mailbox properties page, click Mailbox Features.
   
   
4. Under Message Delivery Restrictions, click View details to view and change the following delivery restrictions:
   
   
   • Accept messages from   Use this section to specify who can send messages to this user.
     
     
     • All senders   This option specifies that the user can accept messages from all senders. This includes both senders in your Exchange organization and external senders. This is the default option. It includes external users only if you clear the Require that all senders are authenticated check box. If you select this check box, messages from external users will be rejected.
       
       
     • Only senders in the following list   This option specifies that the user can accept messages only from a specified set of senders in your Exchange organization. Click Add to display a list of all recipients in your Exchange organization. Select the recipients you want, add them to the list, and then click OK. You can also search for a specific recipient by typing the recipient’s name in the search box and then clicking Search .
       
       
     • Require that all senders are authenticated   This option prevents anonymous users from sending messages to the user. This includes external users that are outside of your Exchange organization.
       
       
   • Reject messages from   Use this section to block people from sending messages to this user.
     
     
     • No senders   This option specifies that the mailbox won’t reject messages from any senders in the Exchange organization. This is the default option.
       
       
     • Senders in the following list   This option specifies that the mailbox will reject messages from a specified set of senders in your Exchange organization. Click Add to display a list of all recipients in your Exchange organization. Select the recipients you want, add them to the list, and then click OK. You can also search for a specific recipient by typing the recipient’s name in the search box and then clicking Search .
       
       
5. Click OK to close the Message Delivery Restrictions page, and then click Save to save your changes.
   
   

The following examples show how to use the Shell to configure message delivery restrictions for a mailbox. For other recipient types, use the corresponding Set- cmdlet with the same parameters.

This example configures the mailbox of Robin Wood to accept messages only from the users Lori Penor, Jeff Phillips, and members of the distribution group Legal Team 1.

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Set-Mailbox -Identity "Robin Wood" -AcceptMessagesOnlyFrom "Lori Penor","Jeff Phillips" -AcceptMessagesOnlyFromDLMembers "Legal Team 1"

Note:
If you're configuring a mailbox to accept messages only from individual senders, you have to use the AcceptMessagesOnlyFrom parameter. If you're configuring a mailbox to accept messages only from senders that are members of a specific distribution group, use the AcceptMessagesOnlyFromDLMembers parameter.

This example adds the user named David Pelton to the list of users whose messages will be accepted by the mailbox of Robin Wood.

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Set-Mailbox -Identity "Robin Wood" -AcceptMessagesOnlyFrom @{add="David Pelton"}

This example configures the mailbox of Robin Wood to require all senders to be authenticated. This means the mailbox will only accept messages sent by other users in your Exchange organization.

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Set-Mailbox -Identity "Robin Wood" -RequireSenderAuthenticationEnabled $true

This example configures the mailbox of Robin Wood to reject messages from the users Joe Healy, Terry Adams, and members of the distribution group Legal Team 2.

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Set-Mailbox -Identity "Robin Wood" -RejectMessagesFrom "Joe Healy","Terry Adams" -RejectMessagesFromDLMembers "Legal Team 2"

This example configures the mailbox of Robin Wood to also reject messages sent by members of the group Legal Team 3.

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Set-Mailbox -Identity "Robin Wood" -RejectMessagesFromDLMembers @{add="Legal Team 3"}

Note:
If you're configuring a mailbox to reject messages from individual senders, you have to use the RejectMessagesFrom parameter. If you're configuring a mailbox to reject messages from senders that are members of a specific distribution group, use the RejectMessagesFromDLMembers parameter.

For detailed syntax and parameter information related to configuring delivery restrictions for different types of recipients, see the following topics:

• Set-DistributionGroup
  
  
• Set-DynamicDistributionGroup
  
  
• Set-Mailbox
  
  
• Set-MailContact
  
  
• Set-MailUser