I know this is more technical than our usual post but on request from several partners I decided to cast it in block for future reference. If you blocking spam but you still get unwanted mail is could be because you did not lock down your o365 mail server and bots and other mail born spammers are able to connect directly to your mail server.
Here is a handy tip:
Follow the steps below to lock down your inbound email flow in Office 365 to only accept email from your SpamTitan IP addresses. This requires you to create a receive connector in Office 365.
- Log on to your Office 365 Exchange Admin Center (EAC).
- Click mail flow in the left menu.
- Click connectors in the top menu to view your connectors.
- Click the add icon and the ‘Select Your Mail Flow Scenario’ window displays. Complete the fields as shown:
- Click Next and the ‘New connector’ window displays.
- In the Name: field change the connector’s name to SpamTitan to Office 365. Click Next.
- In the ‘How do you want to identify the partner organization?’ window:
- Click Use the Sender’s Domain. Click Next.
- Click the add icon and the ‘add domain — Webpage Dialog’ window displays.
- Enter * in the dialog box and click OK.
- Click Next.
- In the ‘What security restrictions do you want to apply’ window:
- Check Reject email messages if they aren’t sent over TLS.ImportantThis option required that outbound TLS is enabled in SpamTitan.
- Select Reject email messages if they aren’t sent from within this IP address range.
- Click the add icon to enter the SpamTitan IP address ranges. Click OK.
- Click Next.
- A summary page displays the information you have entered above. Verify the information is correct and click Save.