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Setting Safe and Blocked Senders in Office 365

To add email addresses or domains to the Safe Sender or Block Sender list in Office 365, follow the steps below:

  1. Login to the O365 Portal at Enter your username as when logging in.
  2. Access the "Mail" section of the portal by clicking the "waffle" icon in the upper left corner and clicking the "Mail" tile.
  3. Click the "Gear" icon in the upper-right. From under the "My app settings" section, click "Mail."
  4. On the left, click "Block or Allow" under the "Accounts" heading.
  5. Enter "" to either the "Safe sender and Recipients" or "Blocked Senders" section. Click the + icon to add the sender to the list.
  6. Click "Save" in the upper left to save the changes to your Blocked or Allowed Senders list.

Safe and Blocked Sender Limitations in Office 365

  • Safe Senders: Must be specified as full e-mail addresses - i.e. adding Safe Sending domains is not supported; Limited to 1000 safe sender e-mail addresses
  • Blocked Senders: Can be either full e-mail addresses or domains (the portion after the @ sign); Limited to 500 blocked senders per mailbox