Error map

WordPress: Could not instantiate mail function WordPress: Mailer Error: Could not instantiate mail function. / wp_mail() failed

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 6 · Platform & cloud 7 · Build & delivery
WordPress: Could not instantiate mail function — WordPress: Mailer Error: Could not instantiate mail function. / wp_mail() failed (Email / SMTP)WordPress: …PHP mail — PHP mail() returns false / emails not delivered (PHP)PHP mail550 5.7.26 — 550 5.7.26 This mail has been blocked because the sender is unauthenticated (SPF/DKIM/DMARC) (Email / SMTP)550 5.7.26421 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…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…sendmail: not found (PHP mail) — PHP: sh: 1: /usr/sbin/sendmail: not found — mail() returns false (Email / SMTP)sendmail: not found…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…PHPMailer: SMTP connect() failed — PHPMailer: SMTP Error: Could not connect to SMTP host. Failed to connect to server (SMTP connect() failed) (Email / SMTP)PHPMailer: SMTP con…redirect_uri_mismatch — OAuth Error: redirect_uri_mismatch (Authentication)redirect_uri_mismat…divergent branches — hint: You have divergent branches and need to specify how to reconcile them. (Git)divergent branchesgpg failed to sign — error: gpg failed to sign the data — fatal: failed to write commit object (Git)gpg failed to signMessageRejected — SES MessageRejected: Email address is not verified. The following identities failed the check in region (AWS)MessageRejectedThere was an error trying to send your message — Contact Form 7: There was an error trying to send your message. Please try again later. (WordPress)There was an error …SMTP 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 5.7.1452 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…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 …552 5.3.4 Message size exceeds fixed limit — SMTP: 552 5.3.4 Message size exceeds fixed maximum message size (Email / SMTP)552 5.3.4 Message s…550 5.7.1 Blocked using zen.spamhaus.org — SMTP: 550 5.7.1 Service unavailable; Client host [203.0.113.5] blocked using zen.spamhaus.org (Email / SMTP)550 5.7.1 Blocked u…550 5.4.1 Recipient address rejected: Access denied — SMTP: 550 5.4.1 Recipient address rejected: Access denied. AS(201806281) [DB5EUR03FT015.eop-EUR03.prod.protection.outlook.com] (Email / SMTP)550 5.4.1 Recipient…missing the MySQL extension — WordPress: Your PHP installation appears to be missing the MySQL extension which is required by WordPress (WordPress)missing the MySQL e…requires at least PHP — WordPress: Your server is running PHP version 7.2 but WordPress 6.x requires at least 7.4 / This plugin requires a newer version of PHP (WordPress)requires at least P…ConnectionRefusedError [Errno 111] (SMTP) — Python: ConnectionRefusedError: [Errno 111] Connection refused — smtplib connect to localhost:25 (Email / SMTP)ConnectionRefusedEr…553 5.7.1 Sender address rejected: not owned by user — SMTP: 553 5.7.1 <noreply@example.com>: Sender address rejected: not owned by user user@example.com (Email / SMTP)553 5.7.1 Sender ad…554 5.7.1 Service unavailable; client host rejected — 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 (Email / SMTP)554 5.7.1 Service u…554 5.4.14 Hop count exceeded - possible mail loop — SMTP: 554 5.4.14 Hop count exceeded - possible mail loop (Email / SMTP)554 5.4.14 Hop coun…SSL: WRONG_VERSION_NUMBER (SMTP port) — SMTP: [SSL: WRONG_VERSION_NUMBER] wrong version number — SMTP over SSL on a STARTTLS port (Email / SMTP)SSL: WRONG_VERSION_…Outbound port 25 blocked — SMTP: telnet smtp.example.com 25 — Connection timed out (cloud provider blocks port 25) (Email / SMTP)Outbound port 25 bl…

Directly related (7)

PHP mailPHP

PHP mail() returns false / emails not delivered

PHP’s mail() function failed or emails never arrive (spam or rejected).

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).

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…

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…

sendmail: not found (PHP mail)Email / SMTP

PHP: sh: 1: /usr/sbin/sendmail: not found — mail() returns false

PHP's `mail()` calls the `sendmail_path` program, but it is not installed or the path in php.ini is wrong.

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.

PHPMailer: SMTP connect() failedEmail / SMTP

PHPMailer: SMTP Error: Could not connect to SMTP host. Failed to connect to server (SMTP connect() failed)

PHPMailer could not open a socket to the SMTP server — wrong host/port/encryption, a blocked port, or a PHP/OpenSSL restriction.

Two steps away (20)

redirect_uri_mismatchAuthentication

OAuth Error: redirect_uri_mismatch

The redirect URI in your OAuth request doesn’t exactly match one registered for the client in the provider’s console.

divergent branchesGit

hint: You have divergent branches and need to specify how to reconcile them.

Git 2.27+ asks you to choose merge, rebase or fast-forward-only when local and remote both have new commits.

gpg failed to signGit

error: gpg failed to sign the data — fatal: failed to write commit object

Commit signing is enabled but GPG couldn’t sign — no TTY for the passphrase, wrong key, or agent not running.

MessageRejectedAWS

SES MessageRejected: Email address is not verified. The following identities failed the check in region

SES refused to send because the From address/domain isn’t verified — or the account is still in the SES sandbox, where recipients…

There was an error trying to send your messageWordPress

Contact Form 7: There was an error trying to send your message. Please try again later.

The form submitted, but wp_mail() failed to send — the server can’t send mail or the mail settings are wrong.

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…

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.

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.

552 5.3.4 Message size exceeds fixed limitEmail / SMTP

SMTP: 552 5.3.4 Message size exceeds fixed maximum message size

The message, including attachments after base64 encoding, is larger than the receiving or sending server accepts.

550 5.7.1 Blocked using zen.spamhaus.orgEmail / SMTP

SMTP: 550 5.7.1 Service unavailable; Client host [203.0.113.5] blocked using zen.spamhaus.org

The receiving server checked your IP in a DNS blocklist (Spamhaus, Barracuda, SORBS…) and refused your mail because it is listed.

550 5.4.1 Recipient address rejected: Access deniedEmail / SMTP

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…

missing the MySQL extensionWordPress

WordPress: Your PHP installation appears to be missing the MySQL extension which is required by WordPress

PHP doesn’t have the mysqli extension loaded, so WordPress can’t talk to the database.

requires at least PHPWordPress

WordPress: Your server is running PHP version 7.2 but WordPress 6.x requires at least 7.4 / This plugin requires a newer version of PHP

WordPress core, a plugin or a theme needs a newer PHP than the server runs.

ConnectionRefusedError [Errno 111] (SMTP)Email / SMTP

Python: ConnectionRefusedError: [Errno 111] Connection refused — smtplib connect to localhost:25

Nothing is listening on the SMTP host and port your script connected to — often `localhost:25` because no host was given and no l…

553 5.7.1 Sender address rejected: not owned by userEmail / SMTP

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.

554 5.7.1 Service unavailable; client host rejectedEmail / SMTP

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.

554 5.4.14 Hop count exceeded - possible mail loopEmail / SMTP

SMTP: 554 5.4.14 Hop count exceeded - possible mail loop

The message passed through too many mail servers (usually over 25), which almost always means two systems forward mail to each ot…

SSL: WRONG_VERSION_NUMBER (SMTP port)Email / SMTP

SMTP: [SSL: WRONG_VERSION_NUMBER] wrong version number — SMTP over SSL on a STARTTLS port

Your client tried to start TLS immediately on a port where the server speaks plain SMTP first (or the reverse), so the handshake…

Outbound port 25 blockedEmail / SMTP

SMTP: telnet smtp.example.com 25 — Connection timed out (cloud provider blocks port 25)

Connections from your server to other mail servers on port 25 time out because your cloud host or ISP blocks outbound SMTP to fig…

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