Bulk email mail server network finder: which network hosts the mail for each address?
In short: Paste email addresses and see, for each domain, its first MX host, that host's IP address and the network and ASN the IP belongs to, from DNS and Team Cymru's IP-to-ASN data. Limit: Reads the domain, never the mailbox: the network of a mail server says nothing about a person's address.
A bulk email mail server network finder reads the domain after the @ in each address, finds its first mail server and maps that server's IP address to a network and ASN. Paste up to 100 unique domains a run, or 500 after a free Google sign-in, and every address gets a row naming its network. It checks the domain, not the mailbox. DNS only. Download the CSV.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. Check your list free nowSee pricing
Sample result
jane@acme.example has its first mail server on Example Network.
- Address
- jane@acme.example
- First MX host
- mx1.acme.example
- IP address
- 192.0.2.10
What this means for you
The network is read from the first mail server's IP. A gateway in front shows the gateway's network, not the mailbox provider's.
- First mail server, IP and ASN
- Filter the list by network
- Gateways and no-mail domains marked
- CSV out, nothing emailed
- MX
- ASN
- DNS
By SimpleVerifier Team · Last updated
Want to split a list by where its mail is hosted?
- Paste it above to see the network behind each address's mail server, with a CSV of every row.
- Upload or paste it at /verify. Every address gets a live mailbox check, and the first 100 email checks are free with a Google sign-in, no card.
How do I find which network hosts the mail for each address on a list?
- Paste email addresses, one per line, or upload a CSV. Addresses are found anywhere in the text, so a whole export works.
- Press Find mail server networks. Only the unique domains are sent, never the mailbox names, 10 a request. DNS only; no mail server is contacted.
- Read each row: the network of the first mail server, with its MX host, IP and ASN. Domains with no mail server are marked.
- Filter by network to split the list, download the CSV, and hand the rest to the mailbox check.
Example
- You enter
- Three addresses:
jane@acme.exampleandtom@globex.example(mail on different networks) andbo@gone.example(no MX record). - You get
- jane: the network of her first mail server, with MX host, IP and ASN. tom: his network. bo: No mail server. Filter by network and download the CSV.
- Limits
- Up to 100 unique domains a run without an account and 500 when signed in with Google. 10 domains a request; MX, address, PTR and IP-to-ASN lookups over DNS only.
What does the network column show?
For each unique domain the tool reads the MX records, takes the first mail server (the one with the lowest priority number), resolves it to an IP address and maps that address to an autonomous system with Team Cymru's IP-to-ASN data. The row shows the network name and ASN, plus the MX host, the IP and a recognised provider where there is one.
The CSV adds the provider, MX host, IP, network and ASN as separate columns, so you can sort and group the list.
How is this different from a provider lookup?
A provider lookup names the mailbox provider from the MX host name, such as Google Workspace or Microsoft 365. This tool names the network the first mail server's IP address sits on, which also reveals hosting companies and smaller providers a name match would miss. Use both: the bulk email provider lookup for the provider name, this one for the network.
A domain behind a security gateway shows the gateway's network, not the mailbox provider's.
What are the flags in a row's detail?
The row's note can say a domain has only one MX host, that all its MX hosts are on one network, or that an address has no reverse-DNS name. They describe the mail setup and are not errors.
For the same lookup on bare domains, use the bulk mail server lookup.
Who uses this tool, and for what?
- Marketers
- Group a list by where each company's mail is hosted.
- Sales teams
- Segment prospects by hosting network or provider family.
- Agencies
- Add a network column to a client list audit and export it as CSV.
- Developers
- Look at the mail hosting spread of a signup export.
What can’t this tool tell you?
- Reads the domain, never the mailbox: the network of a mail server says nothing about a person's address.
- Only the first mail server is shown; domains behind a security gateway show the gateway's network.
- The network name comes from Team Cymru's IP-to-ASN data and can be missing for an address it does not name.
- Up to 100 unique domains a run without an account, 500 signed in.
Common questions
- How do I find which network hosts the mail for an email list?
- Paste the addresses into a bulk email mail server network finder like this one. It reads each address's domain, finds the first mail server and maps its IP address to a network.
- Is this bulk email mail server network finder free?
- Yes. It is a free tool: up to 100 unique domains a run with no account, and up to 500 a run when you sign in with Google, with no card.
- Does it tell me whether the mailbox exists?
- No. It checks the domain, not the mailbox. A mail server on a known network can still reject an address.
- Which mail server does it look at?
- The first MX host, the one with the lowest priority number. Only the first three hosts are resolved to IPs, and the row shows the first.
- Why does a company show a gateway's network?
- Mail sent to a domain behind a security gateway reaches the gateway first, so its network is what the MX records point to.
- Does it connect to the mail server?
- No. It reads DNS and IP-to-ASN data over DNS only, and never opens a connection to a mail server.
Sources
A tidy list can still be full of dead addresses.
Extracting, deduplicating and syntax checks all work on the text of an address. None of them can tell whether the mailbox exists. Only the server that hosts it can answer that, through an SMTP check, and that is what the paid product does.
- Upload the cleaned file as it is: CSVs up to 100,000 rows
- A real SMTP mailbox check on every row, with catch-all detection
- Small list? Starter at $9/mo covers 2,500 emails a month, cancel anytime
Plans from $9 a month, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.