Error map
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 · layer 2, Network
Centre: this error. First ring: errors it is linked with (12). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (12)
ReplyError: NOAUTH Authentication required.
The Redis server requires a password (or ACL user) but the client didn’t authenticate.
WordPress REST API: {"code":"rest_forbidden","message":"Sorry, you are not allowed to do that."} (401/403)
The REST request isn’t authenticated or the user lacks the capability required by the route’s permission_callback.
Received disconnect: Too many authentication failures
Your SSH agent offered too many keys before the right one, and the server cut the connection (MaxAuthTries, default 6).
passwd: Authentication token manipulation error
passwd couldn’t update the password — the root filesystem is read-only, /etc/shadow has wrong permissions/attributes, or a PAM ru…
Laravel: Symfony\Component\Routing\Exception\RouteNotFoundException: Route [login] not defined
Code called route('name') for a route name that doesn’t exist — very often route('login') from the auth middleware in API-only ap…
Nodemailer: Error: Invalid login: 535-5.7.8 Username and Password not accepted (code: 'EAUTH', responseCode: 535)
The SMTP server rejected the credentials passed to Nodemailer.
SMTP: 450 4.7.1 <user@example.com>: Recipient address rejected: Greylisted, see http://postgrey.schweikert.ch/help/example.com.html
The recipient server deliberately rejected the first delivery attempt from an unknown sender (greylisting) and expects a legitima…
SMTP: 530 5.7.0 Must issue a STARTTLS command first / 530 5.7.1 Authentication required
The server will not accept mail until you encrypt the connection (STARTTLS) and/or authenticate, and your client did neither.
DKIM: dkim=fail (body hash did not verify) / signature verification failed
The receiver recomputed the message hash and it does not match the DKIM signature, so the message was altered after signing.
Postfix: warning: SASL authentication failure: cannot connect to saslauthd server: No such file or directory
Postfix could not authenticate a user (inbound) or could not log in to a relay (outbound) because the SASL service or credentials…
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…
SMTP: 535-5.7.8 Username and Password not accepted. Learn more at https://support.google.com/mail/?p=BadCredentials
The server received your login but rejected it — wrong username or password, an unusable password type, or a blocked sign-in.
Two steps away (35)
Azure AD (Entra ID): AADSTS700016 Application not found in the directory
The client ID in your sign-in request doesn’t exist in the tenant you’re authenticating against.
JWT Expired / Invalid Token
The JSON Web Token sent with the request is expired, malformed or signed with a different key, so the API rejects it (usually wit…
OAuth 2.0 Error: invalid_grant
The authorization code, refresh token or credentials sent to the token endpoint are invalid, expired, already used or were issued…
HTTP 401 Unauthorized
The request has no valid authentication credentials — you need to log in or send a valid token.
HTTP 403 Forbidden
The server understood the request but refuses to authorize it — you (or the server process) are not allowed to access this resour…
WordPress: Updating failed. The response is not a valid JSON response.
The block editor saved via the REST API but got HTML or an error page back — broken permalinks, a security plugin/WAF, or PHP out…
Git: Permission denied (publickey). fatal: Could not read from remote repository.
SSH authentication to GitHub/GitLab/Bitbucket failed — no key, wrong key, or the key isn’t added to your account.
Host key verification failed. fatal: Could not read from remote repository.
SSH doesn’t trust the server’s host key — first connection in a non-interactive environment, or the key changed.
WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! (ssh host key changed)
The server’s SSH host key differs from the one saved in ~/.ssh/known_hosts — usually because the server was rebuilt or the IP was…
API Error: Invalid API Key / Incorrect API key provided
The API didn’t recognise the key sent with the request — it’s wrong, revoked, from another environment, or sent in the wrong plac…
user is not in the sudoers file. This incident will be reported.
Your account isn’t allowed to use sudo.
invalid_token: The access token is invalid (JsonWebTokenError: invalid signature / jwt malformed)
A token was sent but the server couldn’t verify it — bad signature, malformed, revoked, or issued for another audience or environ…
HTTP 404 Not Found
The server can’t find anything at the requested URL.
HTTP 405 Method Not Allowed
The URL exists, but it doesn’t accept the HTTP method you used (e.g. POST to a GET-only route).
Azure AD (Entra ID): AADSTS50076 / AADSTS50079 — multi-factor authentication required
A Conditional Access policy requires MFA, but the sign-in flow (often a script, legacy client or ROPC password grant) can’t compl…
SMTP: 534-5.7.9 Application-specific password required. Learn more at https://support.google.com/accounts/answer/185833
The Google account has 2-Step Verification on, so SMTP clients cannot use the normal password; they need an app password (or OAut…
Python: smtplib.SMTPAuthenticationError: (535, b'5.7.8 Username and Password not accepted')
`smtp.login()` was rejected by the server — wrong credentials, wrong password type, or authentication not allowed for that accoun…
Nodemailer: Error: connect ETIMEDOUT 142.250.27.108:465 (code: 'ETIMEDOUT', command: 'CONN')
Nodemailer could not open a connection to the SMTP server before the timeout — a blocked port, wrong host, or network issue.
WordPress / PHPMailer: SMTP Error: Could not authenticate / SMTP connect() failed
The SMTP server rejected the login or couldn’t be reached — wrong credentials, app passwords required, wrong port/encryption, or…
550 5.7.1 Relaying denied / Message rejected as spam / Unauthenticated email not accepted
The receiving (or your outgoing) mail server refused the message — relaying isn’t allowed, the sender isn’t authenticated, or it…
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
The receiving server (often Gmail or Outlook) is temporarily throttling your mail because the volume or reputation of your sendin…
SMTP: 451 4.3.0 Error: queue file write error / 451 Requested action aborted: local error in processing
The server hit an internal problem (disk, database, content filter, DNS) while handling your message and asked you to retry later.
SMTP: 452 4.2.2 The email account that you tried to reach is over quota
The recipient's mailbox has exceeded its storage quota, so the server will not accept new mail for now.
SMTP: 452 4.5.3 Your message has too many recipients / 452 Too many recipients received this hour
The server limits how many recipients a single message or sender may have; yours exceeded it.
550 5.7.26 This mail has been blocked because the sender is unauthenticated (SPF/DKIM/DMARC)
Gmail/Outlook rejected the message because SPF and DKIM didn’t pass for the sender’s domain (DMARC failure).
DKIM: dkim=permerror (no key for signature) / key not found in DNS selector._domainkey
The message is signed with a selector, but the receiver found no DKIM public key in DNS at that selector, so verification cannot…
DMARC: dmarc=fail (p=REJECT) — SPF and DKIM pass but domains are not aligned with the From header
Authentication passed for another domain (your ESP's), but neither the SPF Return-Path domain nor the DKIM `d=` domain matches th…
Postfix: status=deferred (connect to gmail-smtp-in.l.google.com[142.250.27.26]:25: Connection timed out)
Postfix could not reach the remote mail server on port 25, so the message stays in the queue and is retried.
Postfix: status=deferred (Host or domain name not found. Name service error for name=example.com type=A: Host not found, try again)
Postfix could not resolve the destination domain through DNS — the resolver is down or unreachable, or the domain does not exist.
Postfix: fatal: bind 0.0.0.0 port 25: Address already in use
Postfix cannot start its SMTP listener because another process (often Sendmail, Exim or a second Postfix) already uses port 25.
550 5.1.1 The email account that you tried to reach does not exist (User unknown)
The recipient mailbox doesn’t exist on the receiving server — a typo in the address, a deleted account, or a wrong domain.
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
The server refused the connection from your IP because it is blocked by policy, not in the allowed list, or listed on a blacklist.
SMTP: 553 5.7.1 <noreply@example.com>: Sender address rejected: not owned by user user@example.com
The SMTP server only lets an authenticated user send as addresses they own, and the From/envelope sender does not match the login.
SMTP: 550 5.4.5 Daily user sending quota exceeded (Gmail)
The Gmail or Google Workspace account reached its 24-hour sending limit, so it stops accepting outgoing mail until the limit rese…
IMAP: NO [AUTHENTICATIONFAILED] Invalid credentials (Failure)
The IMAP server rejected the login — wrong password, IMAP disabled, an app password required, or basic auth blocked.
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