LOG IN to the Office 365 Administration Console.
Select the Admin | Exchange menu item. The Exchange Admin Center is displayed. Once displayed, in the menu on the left-hand side, CLICK 'mail flow' as shown.
If your Organization hasn't updated their SPF for Office365:
Your organization should have a SPF record for the domain(s) registered with Office 365. When implementing ExchangeDefender with Office 365, this record must be updated in the DNS zone for the relevant domain to include the following:
Remove: v=spf1 include: SPF.PROTECTION.OUTLOOK.COM –all
Replace with: v=spf1 include: EXCHANGEDEFENDER.COM -all
CONFIGURING OUTBOUND SMARTHOST CONNECTOR:
Add a smart host. Add 'outbound.exchangedefender.com' as you see it below.
Once you've entered the smart host hit the 'Save' button. From there you'll be taken to the TLS screen. Keep all options default as shown in the screenshot below. Click NEXT. Add a smart host. Add 'outbound.exchangedefender.com' as you see it below.
Microsoft365 (Office365) can at times, typically during high load or attack on the tenant, randomly block partner organizations from connecting to deliver email. In order to work around this issue, you need to follow the following steps.
Login to Microsoft 365 admin center which is located at https://go.microsoft.com/fwlink/?linkid=2081615
Look across the top and click on "connection filter"
You will now be on the Default connector screen. Click on "connection filtering"
Click on OK.
Click on OK. Click Save.
Congratulations, you're done!