Who handles your leads' email?
Paste a lead list — emails or domains — and see the Google vs Microsoft vs security-gateway split in seconds. Live MX lookup, up to 50 at a time. No signup, no Clay, nothing stored.
Why the recipient's provider matters
Google trusts mail coming from Google infrastructure, and Microsoft trusts Microsoft. Mail that crosses ecosystems gets filtered harder — so a campaign whose leads are mostly Microsoft-hosted while every sending mailbox is on Google quietly loses inbox placement, with zero copy changes to blame. Knowing the provider split of a list before you send lets you match sending infrastructure to it, throttle the risky buckets, and cut the domains that would only produce bounces.
What each result means
- Google Workspace
- MX records point at Google. Filtering is engagement-driven and the most forgiving of the mainstream providers — most B2B startups and agencies live here. Google-to-Google sending keeps you inside one ecosystem, which measurably helps placement.
- Microsoft 365
- MX records point at Exchange Online Protection. The strictest mainstream filter for cold email: authentication must be flawless, and Microsoft junks silently rather than bouncing — low replies from this bucket usually means the spam folder. Common in corporate, finance, legal, and enterprise.
- Security gateway — Proofpoint, Mimecast, Barracuda & co.
- Mail routes through an enterprise filter before it ever reaches the mailbox, so it gets scanned and often quarantined. These leads are harder to reach, not unreachable — the deliverability bar is higher, so they deserve their own low-volume segment. A gateway also tells you something useful: it's a larger, security-conscious org.
- No MX record
- The domain can't receive email — a send is a guaranteed bounce. Receivers start filtering above ~2% bounces, which is the fastest way to burn a sending domain, so these come out of the list before launch.
How it works
Every domain that receives email publishes MX (mail exchange) records in public DNS saying which servers accept its mail — aspmx.l.google.com means Google, *.mail.protection.outlook.com means Microsoft 365, *.pphosted.com means Proofpoint, and so on. This tool resolves those records live and maps them to the provider — the same lookup sales teams build HTTP enrichments in Clay for, without needing Clay, an API key, or a data-provider subscription.