SMTP 550 4.4.7
message expired in the queue
4.4.7 means your message sat in the sending queue until it expired, so the sender gave up. RFC 3463 defines X.4.7 as "delivery time expired". Exchange Online reports it as "Message expired". Every attempt was deferred, so the final NDR combines a 4.x.x code with a failure.
Should you remove the address?
Read the reply text before deciding
Check the domain first. If it no longer accepts mail, remove the address. If the server was only down for a while, the address may be fine on the next send.
Soft bounce. Your sending server retries on its own. Investigate only if it keeps failing.
How it appears
550 4.4.7 QUEUE.Expired; message expired
4.4.7 Message delayed
What causes it
- The recipient's server kept deferring the message, for example through greylisting or rate limiting, until the queue timed out.
- The recipient's server was unreachable for the whole retry period.
- The recipient domain's MX records point at a server that does not answer.
- Microsoft also lists protocol timeouts and too many recipients on one message as causes.
How to fix it
In order — try the first one first.
- Check the recipient address and the domain's mail server before sending again. Resending to a server that never answers will expire the same way.
- Look up the recipient domain's MX records and check that the server answers on port 25.
- If many messages to one domain expire, the recipient's mail server is the problem. Contact them another way.
- Reduce the number of recipients per message.
Who sends it
Any sending server can generate it; Microsoft 365 documents it. It comes from your side after the retry period, not from the recipient.
Microsoft 365
Provider's description Message expired
Microsoft says the sending server tried to deliver the message but didn't complete it before the expiration time, and that it usually indicates a problem on the receiving server.
Common questions
- What does SMTP 550 4.4.7 mean?
- 4.4.7 means your message sat in the sending queue until it expired, so the sender gave up. RFC 3463 defines X.4.7 as "delivery time expired". Exchange Online reports it as "Message expired". Every attempt was deferred, so the final NDR combines a 4.x.x code with a failure.
- Should I retry a 550 4.4.7 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 4.4.7?
- Check the recipient address and the domain's mail server before sending again. Resending to a server that never answers will expire the same way.
- Is 550 4.4.7 a hard bounce or a soft bounce?
- 550 4.4.7 is a soft bounce. It is temporary, and your sending server retries it automatically. Your sending server retries on its own. Investigate only if it keeps failing.
- Should I remove the address after a 550 4.4.7 bounce?
- Check the domain first. If it no longer accepts mail, remove the address. If the server was only down for a while, the address may be fine on the next send.
- Will verifying my list prevent 550 4.4.7?
- Partly. A verification run checks that each domain has a reachable mail server, which catches the domains that have stopped receiving mail for good.
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
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.
Other 550 replies
- 550 5.1.1 — mailbox does not exist
- 550 5.7.1 — message refused by policy
- 550 5.4.1 — recipient address rejected, access denied
- 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 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