Free Email Provider Check

01 · Definition

What is email provider check?

An email provider check identifies which mailbox service receives mail for a given domain — Gmail, Microsoft 365, iCloud, ProtonMail, Zoho, or a custom self-hosted server. The check resolves the domain's MX records via DNS and matches the returned hostnames against a database of known providers, returning the friendly name plus the underlying mail-exchange host.

The tool above runs a live DNS query against the domain you enter (or the domain part of an email address), reads the highest-priority MX record, and surfaces both the provider name and the raw hostname. If the domain has no MX records at all, the tool reports exists: false — the most reliable signal that a domain is not set up to receive mail. Read the in-depth email provider check guide for hostname patterns, segmentation playbooks, and the limits of MX-based detection.

02 · Process

How it works

1. 1Parse the input.Accept either a bare domain (example.com) or a full email address (user@example.com) and isolate the domain part for resolution.
2. 2Query the MX records.Resolve the domain's MX records via DNS and pick the highest-priority hostname. Lower priority numbers win — a priority: 0 record is preferred over priority: 10.
3. 3Match against a provider database.Compare the returned hostname against known patterns: *.gmail-smtp-in.l.google.com is Gmail, *.protection.outlook.com is Microsoft 365, mx*.mail.icloud.com is iCloud, mail.protonmail.ch is ProtonMail, and so on for the rest of the popular providers.
4. 4Return the verdict.If a known provider matches, return its friendly name plus the raw MX record. If the domain has no MX record published, return exists: false. If MX records exist but no provider pattern matches, return the raw hostname for manual identification.

03 · Risk

Why it matters

Knowing the mailbox provider behind a domain shapes how you reach it. Microsoft 365 and Gmail apply different spam scoring, throttle differently, and react to authentication failures with different policies. A list segmented by provider lets you tune sending volumes, dedicated IPs, and warm-up cadence to match what each provider actually wants to see.

The same lookup also flags domains that aren't set up to receive mail — a clean signal for sales hygiene, list cleansing, and vendor due diligence. If your CRM is full of contacts whose domains return exists: false, you're sending into a black hole and burning sender reputation in the process.

04 · Use cases

Common ways to use this tool

• Sales prospecting hygiene. Filter outbound lists to skip domains that cannot receive mail before you spend a credit on enrichment or full email verification.
• List segmentation by provider. Split a marketing list by mailbox provider so you can tune subject lines, sending cadence, and dedicated-IP routing for each cohort.
• Vendor and supplier vetting. Confirm a vendor's email actually routes through the provider they claim — useful for security reviews, KYC, and shadow-IT detection in regulated firms.
• Deliverability triage. When inbox placement drops on a specific cohort, check whether they share a common provider (e.g., a Microsoft 365 reputation issue affecting only Outlook recipients).
• Acquisition due diligence. Map the email infrastructure of an acquisition target before migration to estimate the scope of MX changes, identity migration, and licensing impact.

05 · Interpretation

What to check in the result

The tool returns four things — read them in this order:

• exists flag. If false, the domain has no MX records and cannot receive mail. Drop the address from any sending list immediately and flag the contact for re-verification.
• Provider name. The friendly identifier (Gmail, Microsoft, iCloud, Zoho, ProtonMail, Yahoo). Use it to segment, route, or score the contact in your CRM or ESP.
• MX hostname. The raw record returned by DNS — useful when the provider is custom or the friendly name is missing. The hostname tells you which infrastructure handles the domain.
• MX priority. Lower numbers win. A priority: 0 record is the primary mail exchanger; the tool returns whichever has the lowest number, matching what a real sender would see.
• Custom or unknown providers. If the provider field is missing but exists: true, the domain runs its own mail server. Inspect the hostname directly — it usually identifies the underlying platform.