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Defending against spam or Denial of Service (DOS) attacks from a specific IP address or IP range


Article ID: 171573


Updated On:


Messaging Gateway


You are recieving 1000's of messages from a specific IP or range of IP's and need to block them.


This could be a spam attack or DOS attack.


Messaging Gateway can block an IP address (or CIDR range) from sending email into your environment by temporarily preventing an IP (or CIDR range) from connecting.

  1. In the CC, go to (Reputation -> Bad Senders -> Local Bad Sender IP's)
  2. Click "Add" and type the IPv4 address you wish to block, or a CIDR address range.
  3. Click "Save".
  4. This will block all SMTP connections from that IP address.
  5. You can optionally modify the action in the Actions box.
  6. Select the current action.
  7. Click "Delete".
  8. Click "Add".
  9. Select a new action.
  10. Click "Add Action".
  11. Click "Save".

This IP or CIDR range should be removed from this list once the attack is over. This type of attack typically only occurs for a short period of time.