What a 550 email error code means
A 550 email error is a permanent SMTP refusal. The receiving server has decided not to deliver the message, and it will not queue a retry the way a 4xx temporary failure does. The digits after 550, such as 5.1.1 or 5.7.1, name the family. The sentence on that same line is the cause you change.
| 550 line | What it means | What you change |
|---|---|---|
| 5.1.1 or mailbox unavailable | That recipient address is not a mailbox | Retype the address. Do not keep resending |
| 5.2.2 or quota | The mailbox is full | The recipient frees space or raises the quota |
| 5.7.1 | A policy refused the message: SPF, size, content, or relay | Fix the check named in the sentence |
| 5.7.26 | The From domain had no passing SPF or DKIM | One SPF record, DKIM on, then one test |
| 5.4.1 | The next host did not answer, or the recipient was denied | Confirm the domain's MX, then send one test |
| 5.4.5 | The daily sending quota is used up | Stop. Send again in the next window |
| blocked | A receiving gateway refused the sender or the recipient | Check blocklists, then ask their mail admin |
| relay denied | This SMTP server does not accept your login | Authenticate to the mailbox host on port 587 |
An FTP 550 is a file-permission refusal on an upload, not this mail bounce. Read the human sentence under the code before you edit DNS.
How to fix a 550 for a bad address or a full mailbox
If the code is 5.1.1 or 5.1.10, or the text says user unknown or mailbox unavailable, the address is wrong or the account is gone. Compare it character by character with a message that arrived before. Do not trust the mail app's autocomplete. You know this fix worked when a new test to that address is accepted.
If the code is 5.2.2, or the text says quota or mailbox full, the recipient's box cannot store more mail. They delete mail or the host raises the quota. Sending the same message again does not create space. Inbound mail to your own full mailbox fails the same way, so keep each box under its limit.
How to fix a 550 5.7.1 or 5.7.26 policy rejection
A 550 5.7.1 means the receiving server applied a policy. The sentence may say SPF fail, message too large, content filtered, or unable to relay. Fix only the check it names. For size, send a smaller file. For a content filter, remove the link or file it named, then send one test.
Gmail's 550 5.7.26 means the From domain was not authenticated. Publish one SPF record that lists only the servers allowed to send for that domain. A second SPF record makes both fail. Turn on DKIM in the mail panel, and add DMARC at p=none while you read reports.
In cPanel, Email Deliverability shows whether SPF and DKIM are valid. Wait out the DNS TTL before you judge the test. Relay denied, or a 553 that says the domain is not an allowed recipient host, is a login problem. The mail app is using an SMTP server that does not know the account.
Set the outgoing server to the host that stores the mailbox, turn SMTP authentication on, and use port 587 with TLS. The username is the full email address. You know it worked when one test leaves the outbox and does not come back as 550.
How to fix a 550 caused by missing reverse DNS
Some receivers reject mail when the sending IP has no PTR, or the PTR name does not match the name in the HELO or the SMTP banner. The 550 then mentions reverse DNS, PTR, or a hostname mismatch. On shared mail you cannot edit that PTR from the domain's DNS panel.
Ask the host to set the PTR to the exact mail hostname. The A record for that hostname must point back at the same IP. For a WebJi® mailbox, send that hostname to support@webji.services. The PTR record guide shows the lookup. You know it worked when a lookup of the IP returns that hostname and a new test is accepted.
How to fix a 550 from a blacklisted sending IP
If the bounce names a blocklist, or it says blocked, a gateway refused the sending IP or the domain. The recipient address can still be valid. Look up the sending IP on the blacklist checker before you change SPF again.
Stop the cause first: a compromised mailbox, a forward that loops spam, or a large send from a new IP. Then use that list's own removal form. Delisting is not instant, and a shared IP can be listed because of another account. Do not keep sending from that IP while the listing is open.
How to read the full 550 bounce before you change DNS
Open the non-delivery report and read the SMTP reply at the bottom, not the subject line. Copy three fields: the 550 and the x.y.z code, the remote host name, and the sentence after the code. Change only the family that sentence names.
A 5.4.1 line is a routing or recipient-policy problem, so confirm the domain still has MX records before you touch SPF. A 5.4.5 line means the day's send quota is spent, so you wait. A header-syntax 550 means you retype the To address and do not resend the same draft.
Make one change, then send one test to an address you control. Undo the change if the new bounce shows a different code.
How to stop the next 550 on a business mailbox
These six checks remove the usual 550 families. Each one is a setup step, not another resend of the failed message.
- Publish one SPF record, turn on DKIM, and add DMARC at p=none. In cPanel, Email Deliverability writes the records and shows a failure.
- Ask the host for a PTR that matches the mail hostname, and check the A record points at that IP.
- Check the sending IP on a blocklist once a month, and again after any spam incident.
- Keep each mailbox under its quota so inbound mail is not refused with a 550.
- Warm a new sending IP slowly. Do not mail a large list from a mailbox opened the same day.
- Send through the authenticated SMTP of the mailbox host. Business email hosting with outbound abuse checks keeps a shared IP cleaner than an open relay.
You know the setup worked when a test to an outside mailbox arrives and that test does not generate a new 550.
Frequently Asked Questions
What does a 550 email error mean?
A 550 email error is a permanent refusal from the receiving mail server. The message was not delivered, and the server will not retry it. The numbers after 550, and the sentence beside them, name the mailbox, policy, or sending-IP cause.
How do I fix error 550 in Outlook or Gmail?
Open the bounce and copy the 550 line. In Gmail that line is in the failure message. In Outlook it is in the non-delivery report. If it says relaying denied, set the outgoing server to the host that stores the mailbox, turn on SMTP authentication, and use port 587. Then send one test.
Why are my emails bouncing with 550?
The receiver rejected this message for a permanent reason: a bad address, a full mailbox, a failed SPF or DKIM check, a missing PTR, a blocklist, a relay refusal, or a daily send quota. The sub-code picks which of those it is. Resending the same copy does not clear a 550.
What does a 550 blocked email mean?
Blocked means a filter on the receiving side refused the sender or the recipient. The address can still exist. Check the sending IP on a blocklist, confirm SPF and DKIM pass, and ask the recipient's mail admin if their gateway is holding the domain.
How do I fix 550 5.7.26 for an unauthenticated sender?
Gmail uses 550 5.7.26 when the From domain has no passing SPF or DKIM. Publish one SPF record for the servers that really send, turn on DKIM in the mail panel, and wait for DNS to expire. A second SPF record makes both fail. Send one test after the change.
What is reverse DNS and does it cause 550?
Reverse DNS is the PTR record that maps your sending IP back to a hostname. A missing PTR, or a PTR that does not match the mail hostname, is a common 550. Ask the host to set that PTR. You cannot edit it from the domain's DNS panel on a shared mail IP.
How do I remove my IP from a blacklist?
Stop the cause first: a hacked mailbox, a spam forward, or a bulk blast. Look up the IP, then use that list's own removal form. Removal is not instant, and a shared IP can be listed because of another customer. Do not send more mail from that IP while it is listed.
Does a full mailbox cause 550 errors?
Yes. A full mailbox is usually 550 5.2.2 or a line that says quota exceeded. The recipient has to delete mail or raise the quota. Sending again from your side does not free their space. The same 550 hits mail sent to your own full mailbox.