SMTP 550 5.4.1
recipient address rejected, access denied
SMTP 550 5.4.1 is Microsoft 365's rejection for an address it does not recognise or will not accept mail for. In practice it behaves like 5.1.1 — a hard bounce on a non-existent or disabled mailbox — and is the code you see most often when sending to Outlook and Exchange Online domains.
Should you remove the address?
Read the reply text before deciding
It depends on the text. "Recipient address rejected: Access denied" means remove the address. "Relay Access Denied" is a problem with the recipient's domain setup; the address may be fine once they fix it, but don't keep sending while it fails.
Hard bounce. Do not retry. It will fail every time.
How it appears
550 5.4.1 Recipient address rejected: Access denied. AS(201806281)
550 5.4.1 [[email protected]]: Recipient address rejected: Access denied
What causes it
- The mailbox does not exist in the tenant, or was converted to a shared or disabled account.
- The domain is registered in Microsoft 365 but the specific user was never created.
- A directory-based edge block is refusing mail for unknown recipients in that tenant.
How to fix it
In order — try the first one first.
- Treat it as a hard bounce and remove the address.
- If you expected the address to work, confirm the exact spelling with the recipient — Microsoft tenants do not accept close matches.
- For a whole domain returning 5.4.1, the tenant is likely blocking unknown recipients wholesale, and no address list will get through until someone there allows you.
Who sends it
Mostly Microsoft 365 tenants with Directory Based Edge Blocking turned on, which is common. Other servers use 5.4.1 for routing problems.
Microsoft 365
Reply text Recipient address rejected: Access denied
Microsoft's explanation: the recipient's address doesn't exist.
Microsoft 365
Reply text Relay Access Denied
Microsoft's explanation: the server doesn't accept mail for the recipient's domain, caused by mail server or DNS misconfiguration.
Common questions
- What does SMTP 550 5.4.1 mean?
- SMTP 550 5.4.1 is Microsoft 365's rejection for an address it does not recognise or will not accept mail for. In practice it behaves like 5.1.1 — a hard bounce on a non-existent or disabled mailbox — and is the code you see most often when sending to Outlook and Exchange Online domains.
- Should I retry a 550 5.4.1 error?
- No. 550 is a permanent failure, so the message will never be delivered no matter how many times you try. Remove the address — repeated sends to permanent failures are one of the main signals mailbox providers use to throttle a sender.
- How do I fix SMTP 550 5.4.1?
- Treat it as a hard bounce and remove the address.
- Is 550 5.4.1 a hard bounce or a soft bounce?
- 550 5.4.1 is a hard bounce. The receiving side has said the address can't receive mail, so a retry won't deliver it. Do not retry. It will fail every time.
- Should I remove the address after a 550 5.4.1 bounce?
- It depends on the text. "Recipient address rejected: Access denied" means remove the address. "Relay Access Denied" is a problem with the recipient's domain setup; the address may be fine once they fix it, but don't keep sending while it fails.
- Will verifying my list prevent 550 5.4.1?
- Yes. A mailbox check asks the recipient's server whether the address exists without sending anything, so addresses that would return this code are flagged before the send instead of bouncing against your domain.
Clean the list before the next send.
A bounce report only tells you about the addresses you already mailed. The rest of the list has the same kinds of dead mailboxes in it, and each one becomes a hard bounce recorded against your domain the moment you send.
- A real SMTP mailbox check on every row, before anything is sent
- Dead and mistyped addresses split out, so they never reach your sending tool
- Catch-all, disposable and role addresses flagged alongside
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More Microsoft replies: every Outlook and Microsoft 365 SMTP error, and the 550 5.7.515 bulk sender rules.
Other 550 replies
- 550 5.1.1 — mailbox does not exist
- 550 5.7.1 — message refused by policy
- 550 5.2.1 — mailbox disabled, not accepting messages
- 550 — mailbox unavailable
- 550 5.1.0 — address rejected, other address status
- 550 5.1.10 — recipient not found (Microsoft 365)
- 550 5.1.8 — bad outbound sender (Microsoft 365)
- 550 5.4.5 — daily sending limit exceeded (Gmail)
- 550 4.4.7 — message expired in the queue
- 550 5.7.25 — no PTR record for sending IP (Gmail)
- 550 5.7.26 — blocked, sender unauthenticated (Gmail)
- 550 5.7.27 — SPF authentication failed (Gmail)
- 550 5.7.28 — unusual rate of unsolicited mail (Gmail)
- 550 5.7.23 — SPF violation (Microsoft 365)
- 550 5.7.124 — sender not in allowed senders list (Microsoft 365)
- 550 5.7.509 — DMARC failed, policy reject (Microsoft 365)
- 550 5.7.606-649 — banned sending IP (Microsoft)
- 550 5.7.705 — tenant has exceeded threshold (Microsoft 365)
- 550 5.7.708 — traffic not accepted from this IP (Microsoft 365)
- 550 5.7.750 — blocked from sending from unregistered domains (Microsoft 365)
- 550 5.7.515 — authentication required for high-volume senders (Outlook.com)
- 550 5.7.1 S3140 — IP range on Outlook.com block list
- 550 5.5.0 — Mailbox unavailable (Outlook.com, Hotmail)
- 550 5.7.12 — Sender not authenticated by organization (Microsoft 365)
- 550 5.7.513 — Blocked by the recipient's own block list (Microsoft 365)
Sources
- Source: Microsoft Learn: Email non-delivery reports and SMTP errors in Exchange Online
- Source: RFC 3463: Enhanced Mail System Status Codes
Provider wording is quoted only where the provider publishes it.
Last reviewed 2026-10-22