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Receiving the 550 5.1.8 sender denied error for inbound or outbound emails

This response is received when a connection rule is triggered that has a Permanently reject final action with the value Matches:5.1.8 sender denied and a Sender in list condition.


The rule works by denying all connections originating from or destined to a list of full email address, full domain or IP address. When configuring the rule, the condition is set to Matches: and a Spam Deny list is selected.


If you want to stop receiving the error, you need to remove the associated email address, IP, or domain the Spam Deny list:

  1. Select Products > Email Security > Spam Deny List from the menu on the right side of the console.

  2. Under Select Mailbox: select Global or the mailbox that the Deny List where the entry is located is associated with.

  3. Use the search box to narrow down the list or directly select the entry from the page.

  4. Click Delete.