Is Microsoft 365 a Catch-All Domain? - BounceZero
It Depends - each M365 domain is configured independently

Is Microsoft 365 a Catch-All Domain?

15-25% of M365 business domains have catch-all enabled. You cannot tell from the MX record alone.

Microsoft 365 is a hosting platform - whether a given company's M365 domain is catch-all depends entirely on how their admin configured Exchange Online. All M365 domains share the same *.mail.protection.outlook.com MX records, so you can't tell from DNS alone. BounceZero probes each domain individually to detect catch-all before classifying addresses.

Detect M365 Catch-All Free

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AWS
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for Startups
NVIDIA Inception Program
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Inception
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RapidAPI
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UK Ltd Co.
No. 17153835

Why Microsoft 365 Catch-All Is the #1 B2B Verification Problem

In B2B email marketing, the majority of addresses you're sending to are corporate - hosted on Microsoft 365 or Google Workspace. Consumer providers like Gmail and Yahoo are not catch-all. But corporate domains absolutely can be, and M365's Exchange Online makes it trivially easy for admins to configure catch-all.

The practical effect: your verification tool may return "verified" for a corporate address that doesn't actually exist as a real person's mailbox - it's being caught by the catch-all inbox and silently accepted. Your email lands in an unmanned mailbox, and you never know.

~20%
of M365 business domains have catch-all enabled
0
way to detect catch-all from MX records alone
100%
of M365 domains probed individually by BounceZero

How BounceZero Detects M365 Catch-All

  1. 1. Test probe - BounceZero sends a probe to a known-invalid address at the domain. If Exchange Online accepts it, the domain is catch-all.
  2. 2. Flag accept-all - the domain is marked catch-all and all addresses at it are flagged accordingly.
  3. 3. ML scoring - domain reputation, company signals, DMARC/DKIM configuration, and industry are used to estimate actual deliverability risk.

The result: instead of "verified" (wrong) or "unknown" (useless), you get an accurate risk classification for every M365 address.

Frequently Asked Questions

Is Microsoft 365 catch-all?

M365 is a platform - each domain is configured independently. ~15-25% of M365 business domains have catch-all enabled in Exchange Online. You cannot tell from the MX record alone.

How does BounceZero detect M365 catch-all?

By probing each domain with a known-invalid address. If Exchange Online returns 250 OK, the domain is catch-all. BounceZero then applies ML scoring instead of marking the address as verified.

Do large enterprises have M365 catch-all?

Less commonly than SMBs. Large enterprises with dedicated IT teams usually configure explicit mailboxes. SMBs and professional services firms are more likely to have catch-all enabled. BounceZero checks each domain regardless.

How much does it cost?

$3 per 1,000 verifications. 100 free credits on signup - no credit card required. Catch-all detection included on every domain.

Stop Treating M365 Catch-All as "Verified."

BounceZero detects catch-all per domain and scores with ML. 100 free credits to start.

Start Free Is Google Workspace Catch-All?

Is [provider] a catch-all domain?

Per-provider answers - SMTP behaviour, detection methods, and how BounceZero handles each

Is Yandex catch-all?

Depends - consumer no, Yandex 360 custom domains often yes

Is Fastmail catch-all?

Depends - consumer no, custom domains frequently yes

Is Google Workspace catch-all?

~20% of Workspace domains have catch-all configured

Catch-All Email Verification 2026

What catch-all means, industry prevalence, risk scoring, send vs suppress guide

Is Gmail catch-all?

No - returns 550 for unknown addresses

Is Outlook catch-all?

No - but blocks verifier IPs (Microsoft PTR policy)

Continue through related topics

Catch-all verification guide Email verification guide Email verification research

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