I'm checking up on my email set-up and came across Sender Score as part of my research and tests.

We are sending email through Outlook's mail server. Our original mailfrom domain is fieldworkhub.com. If I put that into Sender Score, I get "no data available".

The DKIM records are validated from Fieldworkhub.onmicrosoft.com. That domain again doesn't have any data. However, it shows around 300 related sending domains, like ACTStoma.onmicrosoft.com which do give you a sender score for some IPs if queried. Why does this not work for our domain? Are we not sending enough emails?

From the email headers, I can find that client-ip= Is that the correct IP to put into the query field? Is there another way to discover sending IPs that doesn't require looking up email headers? For example, checking SPF records? If so, how do I do it?

1 Answer 1


When you're using Office 365 to send out emails, basically, Microsoft determines which IP address it'll use. The SPF record for protection.outlook.com authorizes 491,520 individual IPv4 addresses.

I think you're right about the volume for your domain. I ran your domain name through Cisco's Talos Intelligence and it returns no volume for the past 30 days. As with Talos' reliance on Cisco, Return-Path's SenderScore is depending on data from ReturnPath / ProofPoint's network.

If your looking for reputation data, you might want to look into Feedback loops. This article has a good amount of information to get you started.

As a side note: You may set up your DKIM domain in Office 365 as fieldworkhub.com as opposed to Fieldworkhub.onmicrosoft.com. That way, you'll start authenticating your domain and building your DKIM reputation. Plus if you're going to set your DMARC record to p=reject, it'll help with emails that are being forwarded or sent to mailing lists / Google distribution groups.

  • Thanks a lot for your very helpful answer! I'll have a look at Feedback loops. I've also now implemented DKIM signing from fieldworkhub.com - it works! Commented Jan 22, 2020 at 12:45

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