Free tools/Free recruiter tool
Bulk MX checker: Google, Microsoft 365 or a security gateway?
Paste up to 100 domains or emails and see whether each company runs on Google Workspace or Microsoft 365, and whether Mimecast, Proofpoint or Barracuda sits in front, with what to send first.
- $0to use
- Nosignup
What it does
Paste up to 100 domains to see who runs on Google or Microsoft 365 and who sits behind Mimecast, Proofpoint or Barracuda.
Why it matters: Google and Microsoft filter cold email differently, and a security gateway adds a second filter on top. Our cold email copywriting guide recommends writing a different first touch for each. This checker sorts your list so you know which version each company gets.
Who runs each prospect's email?
Paste up to 100 domains or email addresses. For each one you see whether mail runs on Google Workspace or Microsoft 365, whether a Mimecast, Proofpoint or Barracuda gateway sits in front, and what to send first.
Emails and website links are cut down to the domain. Duplicates and IP addresses are dropped. It reads public DNS records only and never contacts a mail server, so it does not verify addresses.
| Domain | Mail runs on | Gateway | What to send first |
|---|
Advice follows our cold email copywriting guide. A provider marked "from SPF" sits behind a gateway; its SPF record names the mailbox service. Limit: 400 domains an hour per visitor.
What to send each group
| Recipient setup | How hard to reach cold | What to send first |
|---|---|---|
| Microsoft 365 with Mimecast or Proofpoint | Easiest, predictable | One line question, no links |
| Microsoft 365 with Barracuda | Easy, lighter on cold mail | One line question, no links |
| Google Workspace on its own | Medium, strict filtering | Researched one to one opener |
| Google Workspace with Proofpoint or Mimecast | Hardest, two separate filters | Short, relevant, no links |
How it works and what it will not do
- It reads each domain’s public MX record. When a gateway hides the mailbox provider, it reads the domain’s SPF record, which usually names Google or Microsoft.
- It never connects to a mail server or tests a mailbox, so it cannot tell you whether an address exists. Verify addresses with a verifier; compare prices with the verification cost calculator.
- Up to 100 domains per check and 400 an hour per visitor. Your list is not stored; only the public DNS answer for a domain is kept for 24 hours so repeat checks are fast.
Frequently asked questions
How do I tell if a company uses Microsoft 365 or Google Workspace?
Look at its MX record. Google Workspace points to aspmx.l.google.com and Microsoft 365 ends in mail.protection.outlook.com. Paste the domains above to check a whole list at once.
What does a Mimecast or Proofpoint MX mean for cold email?
Mail passes through a security gateway before the inbox. Gateways often open links in a sandbox, so keep the first email short and send it without links or tracking.
Why does a domain show no MX record?
The domain does not receive email, so anything you send there bounces and hurts your sender reputation. Remove it from the list.
Next steps: check your own sending domains with the SPF, DKIM and DMARC checker, vary every line with the spintax checker, and tidy the list with the lead list cleaner.
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