TL;DR
- Outlook.com, Hotmail and Live are Microsoft's own consumer domains. No customer controls their routing, so they are not catch-all in the way a company domain can be.
- Microsoft's public pages do not spell out how its consumer servers answer a check for a missing mailbox, so we don't assert it.
- Expect deliverable or undeliverable when Microsoft answers, and unknown when it refuses the probing IP.
The direct answer
A catch-all is a decision made by whoever runs the domain. For outlook.com, hotmail.com and live.com that is Microsoft, and we found no Microsoft statement saying these domains accept mail for any address. Microsoft's postmaster site is aimed at senders and says it "is not intended to provide extensive support to Outlook.com users" (Outlook.com postmaster site, checked 2026-10-18). It links to a troubleshooting section on SMTP error codes returned by Outlook.com servers, but we could not read that section, so we don't quote codes from it.
That leaves two honest statements. First, a consumer Outlook.com address is not catch-all by anything Microsoft publishes. Second, how its mail servers answer a probe for a missing mailbox is undocumented in the sources we could verify.
What we know from our own checks
On 2026-10-17 we tried five addresses from a home IP. Microsoft's servers answered 550 5.7.1 ... Client host [ip] blocked using Spamhaus. That was a Microsoft mail protection server, which fronts Microsoft 365 tenants, so it is not a clean test of consumer mailboxes, and it was a likely residential-IP listing rather than a verdict on any mailbox. We have not measured consumer Outlook.com on its own, so we don't state how often it is accepted, rejected or deferred.
What the code does is clear: 5.7.x and blocklist wording gives unknown: blocked_by_server, a mailbox-level "does not exist" rejection gives undeliverable: rejected_email, and a temporary 4xx gives unknown: unavailable_smtp. We also keep a minimum gap between sessions to Microsoft servers.
| What the server says | Our result |
|---|---|
| Accepts the address, refuses the random test address | deliverable (risky: low_quality for role addresses such as info@) |
Refuses the address (550 5.1.1 or similar) | undeliverable: rejected_email |
Temporary 4xx answer (deferral, rate limit, greylisting) | unknown: unavailable_smtp after a later retry |
Refuses us for who we are (5.7.x, blocklist or policy text) | unknown: blocked_by_server |
Rules that matter more for senders
The same postmaster page announces that from 5 May 2025, senders of more than 5,000 emails a day to Outlook.com must meet stricter SPF, DKIM and DMARC standards. It says non-compliant mail goes to junk, with rejection to follow once records are fixed. If you send volume to Hotmail users, check your records with the DMARC guide before worrying about the address list.
What to do
- Treat unknown consumer-Microsoft results as unchecked and re-verify them.
- Warm up gradually and watch bounces: bounce thresholds.
- Business addresses on Microsoft use a different system: Is Microsoft 365 a catch-all?
Sources
- Outlook.com postmaster site: checked 2026-10-18
Common questions
Is Outlook.com a catch-all?
Not by anything Microsoft publishes. These are Microsoft's own consumer domains, so no customer can configure them as catch-all.
Is Hotmail the same as Outlook.com?
They are separate consumer domains in the same Microsoft service family, and we treat them the same way when we check them.
Why do I get unknown on Hotmail addresses?
Usually because the server deferred us or refused our IP. Unknown is not a verdict on the mailbox, and unknowns are refunded.