Error map

IMAP: Too many simultaneous connections IMAP: NO [ALERT] Too many simultaneous connections. (Failure)

Email / SMTP · layer 2, Network

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Centre: this error. First ring: errors it is linked with (7). 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.

2 · Network 4 · Application & API 5 · Data 6 · Platform & cloud
IMAP: Too many simultaneous connections — IMAP: NO [ALERT] Too many simultaneous connections. (Failure) (Email / SMTP)IMAP: Too m…fork: retry: Resource temporarily unavailable — fork: retry: Resource temporarily unavailable (process/thread limit) (Linux)fork: retry: Resour…EMFILE — Too many open files (EMFILE) (Linux)EMFILE421 4.7.0 Try again later (rate limited) — 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 (Email / SMTP)421 4.7.0 Try again…Postfix: SASL authentication failed — Postfix: warning: SASL authentication failure: cannot connect to saslauthd server: No such file or directory (Email / SMTP)Postfix: SASL authe…452 4.5.3 Too many recipients — SMTP: 452 4.5.3 Your message has too many recipients / 452 Too many recipients received this hour (Email / SMTP)452 4.5.3 Too many …550 5.4.5 Daily user sending quota exceeded — SMTP: 550 5.4.5 Daily user sending quota exceeded (Gmail) (Email / SMTP)550 5.4.5 Daily use…IMAP: [AUTHENTICATIONFAILED] Invalid credentials — IMAP: NO [AUTHENTICATIONFAILED] Invalid credentials (Failure) (Email / SMTP)IMAP: [AUTHENTICATI…EADDRINUSE — Error: listen EADDRINUSE: address already in use :::3000 (Node.js)EADDRINUSEEPIPE — Error: write EPIPE (Node.js)EPIPEmaxBuffer exceeded — RangeError [ERR_CHILD_PROCESS_STDIO_MAXBUFFER]: stdout maxBuffer length exceeded (Node.js)maxBuffer exceededENOENT — Error: ENOENT: no such file or directory (Node.js)ENOENTECONNRESET — Error: socket hang up / read ECONNRESET (API)ECONNRESET1040 — MySQL ERROR 1040 (08004): Too many connections (MySQL)1040SMTP Error: Could not authenticate — WordPress / PHPMailer: SMTP Error: Could not authenticate / SMTP connect() failed (WordPress)SMTP Error: Could n…550 5.7.1 — 550 5.7.1 Relaying denied / Message rejected as spam / Unauthenticated email not accepted (Email / SMTP)550 5.7.1550 5.7.26 — 550 5.7.26 This mail has been blocked because the sender is unauthenticated (SPF/DKIM/DMARC) (Email / SMTP)550 5.7.26530 5.7.0 Authentication Required — SMTP: 530 5.7.0 Must issue a STARTTLS command first / 530 5.7.1 Authentication required (Email / SMTP)530 5.7.0 Authentic…534 5.7.9 Application-specific password required — SMTP: 534-5.7.9 Application-specific password required. Learn more at https://support.google.com/accounts/answer/185833 (Email / SMTP)534 5.7.9 Applicati…535 5.7.8 Username and Password not accepted — SMTP: 535-5.7.8 Username and Password not accepted. Learn more at https://support.google.com/mail/?p=BadCredentials (Email / SMTP)535 5.7.8 Username …450 4.7.1 Greylisted, please try again later — SMTP: 450 4.7.1 <user@example.com>: Recipient address rejected: Greylisted, see http://postgrey.schweikert.ch/help/example.com.html (Email / SMTP)450 4.7.1 Greyliste…451 4.3.0 Local error in processing — SMTP: 451 4.3.0 Error: queue file write error / 451 Requested action aborted: local error in processing (Email / SMTP)451 4.3.0 Local err…452 4.2.2 Mailbox full / over quota — SMTP: 452 4.2.2 The email account that you tried to reach is over quota (Email / SMTP)452 4.2.2 Mailbox f…SES: Maximum sending rate exceeded — Amazon SES: Throttling — Maximum sending rate exceeded (454 Throttling failure) (Email / SMTP)SES: Maximum sendin…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)SmtpClientAuthentic…DKIM: body hash did not verify — DKIM: dkim=fail (body hash did not verify) / signature verification failed (Email / SMTP)DKIM: body hash did…DMARC fail: SPF and DKIM not aligned — DMARC: dmarc=fail (p=REJECT) — SPF and DKIM pass but domains are not aligned with the From header (Email / SMTP)DMARC fail: SPF and…

Directly related (7)

fork: retry: Resource temporarily unavailableLinux

fork: retry: Resource temporarily unavailable (process/thread limit)

The user or container hit its maximum number of processes/threads (ulimit -u, pids cgroup), so new processes can’t be created.

EMFILELinux

Too many open files (EMFILE)

The process hit its file-descriptor limit — sockets, files and pipes all count.

421 4.7.0 Try again later (rate limited)Email / SMTP

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…

Postfix: SASL authentication failedEmail / SMTP

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…

452 4.5.3 Too many recipientsEmail / SMTP

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 5.4.5 Daily user sending quota exceededEmail / SMTP

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: [AUTHENTICATIONFAILED] Invalid credentialsEmail / SMTP

IMAP: NO [AUTHENTICATIONFAILED] Invalid credentials (Failure)

The IMAP server rejected the login — wrong password, IMAP disabled, an app password required, or basic auth blocked.

Two steps away (19)

EADDRINUSENode.js

Error: listen EADDRINUSE: address already in use :::3000

Another process is already listening on that port.

EPIPENode.js

Error: write EPIPE

Node wrote to a pipe or socket whose other end was already closed.

maxBuffer exceededNode.js

RangeError [ERR_CHILD_PROCESS_STDIO_MAXBUFFER]: stdout maxBuffer length exceeded

child_process.exec/execSync produced more output than its buffer allows (default 1 MB).

ENOENTNode.js

Error: ENOENT: no such file or directory

A file or directory the program tried to open doesn’t exist at that path.

ECONNRESETAPI

Error: socket hang up / read ECONNRESET

The other side closed the TCP connection abruptly while your client was still using it.

1040MySQL

MySQL ERROR 1040 (08004): Too many connections

MySQL reached `max_connections` and refuses new clients.

SMTP Error: Could not authenticateWordPress

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 5.7.1Email / SMTP

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…

550 5.7.26Email / SMTP

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).

530 5.7.0 Authentication RequiredEmail / SMTP

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.

534 5.7.9 Application-specific password requiredEmail / SMTP

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…

535 5.7.8 Username and Password not acceptedEmail / SMTP

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.

450 4.7.1 Greylisted, please try again laterEmail / SMTP

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…

451 4.3.0 Local error in processingEmail / SMTP

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.

452 4.2.2 Mailbox full / over quotaEmail / SMTP

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.

SES: Maximum sending rate exceededEmail / SMTP

Amazon SES: Throttling — Maximum sending rate exceeded (454 Throttling failure)

You are sending faster than your Amazon SES account's per-second limit, so SES throttles the requests.

SmtpClientAuthentication is disabled for the TenantEmail / SMTP

SMTP: 535 5.7.139 Authentication unsuccessful, basic authentication is disabled / SmtpClientAuthentication is disabled for the Tenant

Microsoft 365 turned off password-based SMTP AUTH for your mailbox or tenant; your client must use OAuth or the setting must be r…

DKIM: body hash did not verifyEmail / SMTP

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.

DMARC fail: SPF and DKIM not alignedEmail / SMTP

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…

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