Step 1: Open the Exchange Admin Center.
Step 2: Expand the protection and click on + sign
Step 3: Now you will a list of possible rules. Select Restrict Messages by Sender or Recipient as shown below.
Step 4: Give the name to this rule and click on more options to expand more options
Step 5: Now the rule creation window will look like this
Step 6: In Apply this rule ‘if select his sender is locate’ or Outside the Organization as per your requirement
Step 7. Click ok then click on add condition and select “The Sender” “is this person”.
Step 8. In the Select members window type the email address in the checknames. If you have more than one email address then make sure they are separated with semicolon (;). Paste them all and type semicolon for the last email address, they all will be moved to add. Click ok.
Step 9. Now all email addresses will show next to the rule condition.
Step 10. In Do the following action select Block the message. Now we get 3 options. I will select “Delete the message without notifying anyone” to avoid queue building for spams.
Step 11: Set the priority of the rule and Click save.
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