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“550 relay not permitted” means the SMTP server has refused to forward your message. The server does not recognise your client as authorised to send to the recipient’s domain. In most cases, the fix is to enable SMTP authentication, use the provider’s outbound submission host on port 587 (STARTTLS) or 465 (implicit TLS), and make the From address match the authenticated mailbox. If you operate the server, you must also permit the authenticated account or approved sending IP in its relay policy without turning it into an open relay.
Use the checklist below in order. It starts with client settings because missing authentication and an incorrect host or port are the most common causes, then covers sender-address, DNS, Exchange/Jira, and server-side policy problems.
What the SMTP 550 relay error means
SMTP servers distinguish between submission (a user handing an outgoing message to a provider) and relay (a server forwarding that message toward another domain). A server normally accepts mail for domains it hosts. It should only relay mail to other domains for a client it can identify and trust.
The refusal usually occurs when the client reaches the recipient stage, after EHLO and MAIL FROM, and sends RCPT TO for a domain that the server does not host. The server then returns a permanent policy error instead of accepting the message. This is generally an authorisation or configuration problem, not evidence that your message has been blocked for poor reputation.
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| Reply text | What it indicates |
|---|---|
550 relay not permitted |
The server will not relay for the current connection or account. |
550 5.7.1 Unable to relay |
A policy refusal commonly seen with Exchange and Jira-related mail setups. |
550 5.7.1 Relaying denied or relaying denied (not permitted) |
The sender is not authorised to use that server for the destination domain. |
554 5.7.1: Relay access denied |
The same class of relay-policy refusal returned with a different SMTP status code. |
The exact wording varies by product. The important clues are the 550 or 554 status and the phrase “relay,” “relaying,” or “unable to relay.”
Quick triage before changing settings
- Identify who controls the SMTP host. Is it your mailbox provider, web host, company mail server, an application on your network, or a third-party relay? The correct hostname and policy come from that operator.
- Check whether every recipient fails. A failure only for external recipients points strongly to relay authorisation. A failure for local recipients may indicate a broader authentication, address, or connectivity problem.
- Record the complete response. Save the status code, enhanced code such as
5.7.1, server name, timestamp in UTC, and the application that generated it. These details let an administrator find the matching log entry. - Confirm which account is actually being used. Mail applications can retain an old password, select a different account, or send through a default account you did not intend to use.
- Check the sender domain and recipient domain. A server may accept mail for one domain but refuse to relay it to another, especially when an alias or forwarding address is involved.
Fixes for the most common causes
1. Turn on SMTP authentication
Unauthenticated connections are the leading cause of this error. In your mail client or application, open the account’s Outgoing server, SMTP, or Server settings page. Select the option labelled My outgoing server requires authentication, SMTP AUTH, or equivalent. Choose the setting that uses the same credentials as the incoming account unless your provider explicitly supplies separate credentials.
Use the complete email address as the username, not only the part before the @, unless the provider documents a different format. Re-enter the password carefully and save the account. Send a new test message rather than repeatedly retrying an old queued message; some applications preserve the original unauthenticated connection.
If authentication itself fails, stop troubleshooting relay permissions and fix the credential or connection problem first. A server cannot authorise relay for a session that never successfully authenticates.
2. Use the provider’s outbound submission host
Do not assume that the host named in your domain’s MX record is suitable for sending. MX records identify servers that receive mail for a domain; a receiving MX host may deliberately refuse client submission and relay. Use the SMTP hostname listed in your provider’s account documentation or control panel.
Check for spelling errors, an obsolete hostname, and a host belonging to a different account. If a web application and a desktop client use different providers, each may require its own SMTP host. Changing only the password will not correct a connection to the wrong server.
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3. Select the correct port and encryption mode
| Port | Typical use | Encryption setting | What to do |
|---|---|---|---|
| 25 | Server-to-server SMTP transport | May begin unencrypted and optionally negotiate STARTTLS; client authentication is often restricted | Do not use it for ordinary mailbox submission unless your administrator specifically requires it. |
| 587 | Authenticated client submission | STARTTLS (sometimes shown as “TLS” or “explicit TLS”) | Use this as the normal first choice for applications and mail clients. |
| 465 | Authenticated submission with encryption from the first byte | Implicit TLS (sometimes shown as “SSL/TLS”) | Use only when your provider documents port 465 and implicit TLS. |
A common mistake is selecting port 25 while enabling authentication. Many relays do not offer or permit client AUTH on that port and respond with 550 5.7.1. Set the port and encryption mode as a pair: port 587 with STARTTLS, or port 465 with implicit TLS. Do not combine port 465 with a STARTTLS option, or port 587 with an implicit-SSL option, unless the provider explicitly says to do so.
4. Make the From address match the authenticated account
Some servers permit authenticated submission only when the envelope sender and visible From address belong to the authenticated account or to an alias that account is allowed to use. For example, signing in as alex@example.net and sending as billing@other-domain.test can trigger a relay refusal even when the password is correct.
For the first test, set both the account username and From address to the same full mailbox address. If that succeeds, add the alternate address as a verified alias or request “send as” permission from the administrator. Changing the display name does not change the address that the server evaluates.
5. Check recipient-domain and sender-domain policy
Exchange environments and hosted relays can apply rules that block a sender domain, require a specific connector, or allow relay only to selected recipient domains. A message can therefore authenticate successfully and still receive 550 5.7.1 Unable to relay at the recipient stage.
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6. Correct SPF, DKIM, DMARC, and sending-IP authorisation
DNS-based sender controls do not replace SMTP authentication, but a relay may use them as an additional policy check. Publish an SPF record that includes every service and server legitimately sending for the domain. Ensure the sending service signs with DKIM when required, and set DMARC alignment rules that match the visible From domain.
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Confirm that the public IP connecting to the relay is the IP you intended to use and that it is included in the provider’s permitted-sender list when such a list exists. Check whether the IP appears on relevant blocklists. A blocklist issue is distinct from a basic relay denial, but some providers combine these checks and return a similar 5.7.1 response.
After changing DNS, allow time for the new records to propagate according to their TTL. Test the record from more than one resolver and verify that old SPF mechanisms have not created multiple SPF records or exceeded lookup limits.
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Application-specific checks
Desktop mail clients
Open the account’s outgoing-server page and verify, together, the SMTP host, port, encryption, authentication method, username, and From address. Remove duplicate accounts that use the same address with different SMTP settings; the client may be selecting the wrong one. Clear any saved password and enter it again if the application reports an authentication error.
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Set the SMTP library’s host, port, TLS mode, username, password, and sender address explicitly rather than relying on defaults. Port 25 is a frequent default in application frameworks and is often unsuitable for submission. Make sure the application is not using a server’s MX hostname or the address of a local-only mail daemon.
Use a dedicated mailbox or approved service account for automated mail, and grant it permission to send from the address configured in the application. Keep credentials out of source code and logs. If the application runs behind a NAT gateway, give the relay administrator the gateway’s public egress IP, not the machine’s private address.
Exchange and Jira Server installations
For an on-premises Exchange or Jira Server deployment, the receiving connector or SMTP relay component must be configured to accept the application’s connection. Check whether the connector requires authenticated submission, certificate-based trust, or an allowed source IP. Verify that the connector permits relay to external recipient domains and that the sender address is an accepted address for the account.
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Do not broadly permit an entire network unless necessary. A narrowly scoped source-IP or authenticated-account rule reduces the risk of creating an open relay. Changes to connectors may require a service reload or restart according to the product’s administration procedure.
Testing the SMTP conversation directly
A direct protocol test separates an application’s settings from the server’s policy. Run it from the same host and network that produces the error, because the relay may authorise one source IP and reject another. Replace the hostname with the outbound SMTP host documented by your provider:
openssl s_client -starttls smtp -connect smtp.example.net:587 -crlfWhen the TLS session is established, type the following commands one at a time:
EHLO test.example.net
AUTH LOGIN
MAIL FROM:<user@example.net>
RCPT TO:<recipient@external.example>
QUITThe server will normally issue prompts after AUTH LOGIN for base64-encoded credentials. Do not paste real credentials into a ticket, chat, shell history, or published transcript. If the TLS handshake fails, investigate the host, port, certificate trust, firewall, or TLS mode. If AUTH fails, correct the username, password, authentication method, or account policy. If AUTH succeeds but RCPT TO still returns a 550/554 relay error, focus on the From address, recipient-domain policy, allowed source IP, and connector rules.
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For an implicit-TLS service on port 465, use:
openssl s_client -connect smtp.example.net:465 -crlfDo not use -starttls smtp with an implicit-TLS endpoint.
Read the server logs at the rejection stage
Find the log entry that matches the test timestamp and connecting IP. On Postfix or Sendmail systems, administrators commonly inspect /var/log/maillog or /var/log/mail.log; exact paths depend on the operating system and logging configuration. Exchange installations expose SMTP protocol or connector logs through their administration and diagnostic tools.
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- Rejected before AUTH: the host, port, TLS negotiation, or connection policy is wrong.
- AUTH rejected: credentials, authentication method, account status, or an authentication requirement is wrong.
- MAIL FROM rejected: the sender address, domain, or account’s send-as permission is invalid.
- RCPT TO rejected with 550/554 relay text: the session is not allowed to relay to that recipient domain, or the source IP and connector policy do not match.
Share the relevant log lines with the server administrator, redacting passwords, tokens, message contents, and personal data. The SMTP status line and rule name are usually enough to identify the failing policy.
Server-side relay configuration
If you administer the relay, verify four controls in this order:
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- Trusted sources: authenticated users or explicitly approved source IPs must be included in the relay policy.
- Destination policy: the relay must allow delivery to the intended external domains while still rejecting unauthorised destinations.
- Sender restrictions: the account or source must be allowed to use the envelope sender and visible
Fromaddress supplied by the application.
Postfix and Sendmail implement these controls through different configuration files and access databases, and Exchange uses receive connectors and transport permissions. Exact directives and menus vary by release, so apply the syntax documented for your installed version. After changing policy, reload or restart the affected service as required and repeat the direct SMTP test.
Never solve the error by allowing unrestricted relay from the internet. An open relay can be abused to send large volumes of spam and may quickly damage the server’s reputation or exhaust resources. Prefer authenticated submission, a tightly limited source-IP range, or both.
Why a correct password may still produce 550
Authentication proves who connected; it does not automatically grant every sending permission. The server may still reject the transaction when:
- the client authenticated to a receiving-only host;
- the connection used port 25 instead of the provider’s submission port;
- the visible or envelope sender is not an address the account may use;
- the destination domain is outside the connector’s permitted scope;
- the connecting public IP is not on the approved list;
- the domain’s SPF, DKIM, DMARC, or other sender policy fails a provider-specific check; or
- an Exchange or Jira connector is configured for internal delivery only.
Decision table for isolating the fault
| Observed result | Most likely area | Next action |
|---|---|---|
| No connection or TLS handshake | Hostname, port, firewall, or encryption mismatch | Use the documented submission host; pair 587 with STARTTLS or 465 with implicit TLS. |
| Server never advertises AUTH | Wrong service or port | Move from a receiving/MX host or port 25 to the provider’s authenticated submission endpoint. |
| AUTH returns an error | Credentials or account policy | Use the full email username, reset or re-enter the password, and verify that SMTP AUTH is allowed. |
| AUTH succeeds; MAIL FROM is refused | Sender address or send-as permission | Send from the authenticated mailbox, then request alias/send-as permission if needed. |
| AUTH and MAIL FROM succeed; RCPT TO returns 550/554 | Relay, destination, or source-IP policy | Check connector relay scope, recipient-domain restrictions, approved IPs, and DNS sender policy. |
| Only one application fails | Application-specific settings | Compare that application’s host, port, TLS mode, credentials, and sender with a known-working client. |
| Every client from one network fails | Public-IP or network policy | Identify the NAT egress IP and ask the relay administrator whether it is authorised or blocked. |
When to contact the mail provider or administrator
Escalate after you have verified the outbound host, port, TLS mode, credentials, and matching sender address. Include the exact SMTP response, enhanced status code, UTC timestamp, connecting public IP, authenticated username (not its password), recipient domain, and the output from a redacted test. Ask which submission endpoint and authentication method the account should use, whether external relay is enabled, and whether the source IP or sender address must be approved.
If the administrator says the account is authorised but the server still returns 550, provide the log’s rejection stage and rule name. That evidence distinguishes an account problem from a connector, destination-domain, or DNS-policy problem and avoids repeated password resets that cannot fix relay policy.
Quick Recap
Preventing the error after it is fixed
- Document the approved SMTP hostname, port, TLS mode, sender address, and account owner.
- Monitor expiry of passwords, certificates, and DNS records used by the sending service.
- Keep SPF, DKIM, and DMARC records aligned with the systems that actually send mail.
- Review relay and connector permissions whenever an application, domain, or public IP changes.
- Test one internal and one external recipient after planned mail-server changes.
- Keep relay rules narrow and review them periodically so an old host or address does not remain trusted indefinitely.
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