550 5.4.1 Recipient address rejected: Access denied Email / SMTP Origin: Network Last updated 4 Nov 2026

SMTP: 550 5.4.1 Recipient address rejected: Access denied. AS(201806281) [DB5EUR03FT015.eop-EUR03.prod.protection.outlook.com]

Microsoft 365 / Exchange Online rejected the message because the recipient address does not exist in that tenant (Directory Based Edge Blocking).

Exact message you may see 550 5.4.1 Recipient address rejected: Access deniedRecipient address rejected: Access denied. ASDBEB Directory Based Edge Blockingprotection.outlook.com 550 5.4.1550 5.4.1 Recipient address rejected
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Seen on: SMTP

Meaning

Since 2018 Exchange Online rejects mail for unknown recipients at the edge. The address is misspelled, deleted, not yet synced from on-premises Active Directory, or the mail flow connector is wrong. Ask the recipient for the correct address, or fix the sync.

Common causes

  • Typo or non-existent recipient address
  • User deleted or never licensed in Microsoft 365
  • Hybrid sync (Azure AD Connect) not yet replicated the mailbox
  • Accepted domain set to Internal Relay without a connector
  • Distribution group restricted to internal senders

⚡ Quick fix

  1. Verify the exact address with the recipient
  2. Admins: confirm the mailbox exists in the Microsoft 365 admin centre
  3. Check accepted domain type (Authoritative vs Internal Relay)

Detailed fix by platform

PowerShell

  1. Get-Recipient user@contoso.com in Exchange Online PowerShell confirms whether the address exists

How to diagnose

  1. Address — Spelled correctly?
  2. Tenant — Mailbox exists and is licensed?
  3. Sync — Hybrid/AD sync complete?

🔧 Still not fixed?

Many errors look alike. If the steps above didn’t solve it, one of these is probably what you’re facing:

Where this error sits

Origin: Network. Errors that are often confused with or caused by this one (click to open):

421 4.7.0 Try again later (rate limited) — SMTP: 421 4.7.0 Our system has detected an unusual rate of unsolicited mail originating from your IP address. Mail sent from your IP address has been temporarily rate limited (Email / SMTP)421 4.7.0 Try again l…450 4.7.1 Greylisted, please try again later — SMTP: 450 4.7.1 <user@example.com>: Recipient address rejected: Greylisted, see http://postgrey.schweikert.ch/help/example.com.html (Email / SMTP)450 4.7.1 Greylisted,…451 4.3.0 Local error in processing — SMTP: 451 4.3.0 Error: queue file write error / 451 Requested action aborted: local error in processing (Email / SMTP)451 4.3.0 Local error…550 5.1.1 — 550 5.1.1 The email account that you tried to reach does not exist (User unknown) (Email / SMTP)550 5.1.1550 5.7.1 — 550 5.7.1 Relaying denied / Message rejected as spam / Unauthenticated email not accepted (Email / SMTP)550 5.7.1554 5.7.1 Service unavailable; client host rejected — SMTP: 554 5.7.1 Service unavailable; Client host [203.0.113.5] blocked / 554 5.7.1 <mail.example.com>: Client host rejected: Access denied (Email / SMTP)554 5.7.1 Service una…SmtpClientAuthentication is disabled for the Tenant — SMTP: 535 5.7.139 Authentication unsuccessful, basic authentication is disabled / SmtpClientAuthentication is disabled for the Tenant (Email / SMTP)SmtpClientAuthenticat…550 5.4.1…

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