What to do after successfully setting up DMARC?

[Dascalargo]

I was able to get DMARC set up and have verified using a couple of different third-party tools that I've done it correctly. I'm receiving the reports. Fine and dandy. Now what?

So far, the reports have all passed, but then today I get one that fails. It failed DMARC, SPF, and DKIM. How does that information help me? The IP shown goes to Mailgun, a service I don't use, but I assume one of my providers does. But there's nothing to tell me which email it was or which app or service sent it, so I don't know how to correct the problem.

What is the next step?

[onescales]

first you need to make sure that no other app or 3rd party is actually using mailgun that you are not aware of. if ok, you can consider blacklisting from your email provider and open a ticket with them

[Dascalargo]

But how do you know that? Apps don’t tell us what provider they’re using. Do we even know what provider Shopify itself uses?

[onescales]

shopify email comes from shopifyemail.com and is written in there documentation and when you send an email that is not authenticated you can see this.

[Dascalargo · Accepted solution]

Yeah, if that had been the case, I wouldn't be asking the question. It's not the same thing. The DMARC reports don't show the "from" address. They show the IP addresses, and none of the IPs in the reports resolve back to anything obviously related to Shopify. I'm assuming Shopify either has space on another company's servers or uses another email service, or something like that.

I'm not certain, but based on the size of the company, process of elimination, and a bit of Googling, I'm guessing that the Twilio Sendgrid listings I see are the ones send by Shopify. Would have been nice to have someone provide that info, though, so I know which sources are working and which aren't. 

Hopefully this is helpful for someone else out there.