Christian splits lists by MX record, claims 6.5x replies
A free Google DNS tool reads a prospect's mail host, CRM and ad stack before you send a single email.
Christian says his campaigns see 6.5x more replies from prospects on Google than from prospects on Microsoft, and that the split is visible for free in public DNS before anything goes out. His fix is to sort every list by the MX record, send the Google half from Google inboxes, and give the Microsoft half its own copy kept under 40 words.
The lookup
The tool is Google's own Admin Toolbox Dig. Type in a prospect domain, click MX, and read the host. `ASPMX.L.GOOGLE.COM` or `SMTP.GOOGLE.COM` means Google Workspace. `MAIL.PROTECTION.OUTLOOK.COM` means Microsoft. `PPHOSTED.COM` or `MIMECAST.COM` means a security filter, Proofpoint or Mimecast, reads every email before the prospect does. That is the inbox your email lands in, known before you send.
Then click TXT. The line starting `V=SPF1` lists every tool allowed to send email as that company. Christian's reads: `_SPF.SALESFORCE.COM` for Salesforce, `HUBSPOTEMAIL.NET` for HubSpot, `MAIL.ZENDESK.COM` for the support desk, `SERVERS.MCSV.NET` for Mailchimp newsletters. The rest of the TXT records carry verification strings from anything that made the company prove domain ownership, including `FACEBOOK-DOMAIN-VERIFICATION` for advertisers, `ATLASSIAN-DOMAIN-VERIFICATION` for Jira or Confluence, `DOCUSIGN=`, and `OPENAI-DOMAIN-VERIFICATION` for companies that have set up ChatGPT.
Running it at list scale
Christian's instruction for doing this on a whole list is to export the CSV, open Claude Code and ask it to run an MX and TXT lookup on every domain, adding what it finds as columns. He describes it as a few lines of code that costs nothing. No alert fires at the target company, because DNS is public by design.
The practical use he lays out is three cuts from one lookup. MX tells you Google or Microsoft, so you split the campaign. SPF tells you their CRM, which is how you build a list of a competitor's customers. TXT tells you who is running ads and who is already paying for AI tools, which he treats as a budget signal.
What to trust here
The lookup is verifiable on your own list in an afternoon, and Christian suggests starting by running your own domain to see what competitors can see. The 6.5x number is a different thing. It is his agency's own figure, posted with no send volume, no list size and no time period attached, so treat it as one operator's claim rather than a benchmark. The cheap test is to tag your existing list by mail host and compare reply rates you already have, which costs nothing and settles it with your own data.
SPF TELLS YOU THEIR CRM, SO YOU FIND YOUR COMPETITOR'S CUSTOMERS
WE SEE 6.5X MORE REPLIES FROM PROSPECTS ON GOOGLE THAN FROM PROSPECTS ON MICROSOFT
Know what is landing before you burn another domain
One email a day. Under three minutes. What the operators found out yesterday.