MX host decoder: which provider is aspmx.l.google.com or mail.protection.outlook.com?
In short: Paste a list of MX hosts, MX records or SPF include hosts and get the mail provider behind each one, marked as a mailbox provider, a security gateway or a forwarding service. Limit: It matches host names against fixed rules and does not look anything up, so it cannot see a domain's live records.
Paste MX hosts, full MX records or SPF include hosts, one per line, and the decoder names the provider behind each: aspmx.l.google.com is Google Workspace, mail.protection.outlook.com is Microsoft 365 and mx.zoho.com is Zoho Mail. Each is marked as a mailbox provider, a security gateway or a forwarding service.
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
Seven pasted lines read as 7 hosts, 6 of them recognised: Google, Microsoft and Zoho.
- Hosts recognised
- 6 of 7
- Google Workspace
- 3
- Microsoft 365
- 2
What this means for you
Knowing the provider is one step; whether each address bounces is a mailbox check.
- MX hosts and records
- SPF include hosts
- Gateways marked
- Table as a CSV
- MX
- SPF
- Provider
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
Know the provider? Now see which addresses at it bounce.
- Decode the hosts here, or look up whole domains with the bulk email provider lookup.
- 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 decode an MX host?
- Paste the hosts, one per line. A bare host, a line such as
10 aspmx.l.google.com.or a full DNS line all work. - Paste an SPF record or
include:hosts too if you have them; each include is read as its own host. - Press Decode the hosts and read the table: the host, the provider, what kind of service it is and where it was found.
- Download the table, and look up any host that is not recognised with the email provider lookup.
Example
- You enter
- Seven lines: the Google MX hosts aspmx.l.google.com and alt1.aspmx.l.google.com, a Microsoft 365 MX host, mx.zoho.com, an SPF record with two includes (spf.protection.outlook.com and _spf.google.com) and mx1.example-host.test.
- You get
- 7 hosts read, 6 recognised: Google Workspace 3, Microsoft 365 2 and Zoho Mail 1. mx1.example-host.test is not recognised.
- Limits
- Runs in your browser; nothing is uploaded. It matches host names against fixed rules and does not look up live records.
How does it know the provider?
It matches the end of each host against the provider rules the email provider lookup uses: for example a host ending in mail.protection.outlook.com is Microsoft 365 and one ending in google.com is Google Workspace. The rules follow providers' published MX host names and our B2B provider study.
SPF include hosts are checked against the SPF rules first, so spf.protection.outlook.com reads as Microsoft 365 and _spf.google.com as Google Workspace.
What is a security gateway or a forwarding service?
A security gateway such as Proofpoint or Mimecast sits in front of the real mailbox and filters mail first, so the MX host names the gateway, not the provider that holds the mailbox. A forwarding service such as Cloudflare Email Routing passes mail on to another inbox. The table marks which kind each host is. The secure email gateway checker works on whole lists of domains.
Why is a host not recognised?
The rules cover well-known mailbox providers, gateways and forwarders. A company that runs its own mail server, or a smaller provider, has a host that is not in them. That is not an error, and it does not mean the domain cannot receive mail. The bulk MX lookup shows the live MX records for a list of domains.
Who uses this tool, and for what?
- Cold emailers
- Decode the MX hosts from a DNS export to see how a list splits between Google, Microsoft and others.
- IT admins
- Check what an inherited MX or SPF record points at before a migration.
- Deliverability consultants
- Tell a gateway host from a mailbox host when reading a client's DNS.
What can’t this tool tell you?
- It matches host names against fixed rules and does not look anything up, so it cannot see a domain's live records.
- Behind a security gateway the MX host names the gateway, not the provider that holds the mailbox.
- A host that is not recognised may be a company's own server or a smaller provider.
- It says nothing about whether an address at the domain exists.
Common questions
- What provider is aspmx.l.google.com?
- Google Workspace. Hosts ending in google.com or googlemail.com are Google's mail servers.
- What provider is mail.protection.outlook.com?
- Microsoft 365. A host such as example-com.mail.protection.outlook.com is the Microsoft 365 address for a company's domain.
- Can I paste a full DNS line?
- Yes. A line such as
example.com. 300 IN MX 10 mx.zoho.com.is read as the host mx.zoho.com. - Does it look anything up?
- No. It matches the names you paste against a fixed set of rules, in your browser, so it cannot see a domain's live records.
- Does it tell me who hosts a domain's mail?
- Only for the hosts you paste. Behind a gateway the host names the gateway, not the mailbox provider. The email provider lookup reads a domain's own records.
- Does it say whether an address exists?
- No. Knowing the provider says nothing about whether a mailbox exists; that needs a mailbox check.
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.