Error map
SPF PermError: too many DNS lookups SPF: spf=permerror — Too many DNS lookups (limit is 10)
Email / SMTP · layer 2, Network
Centre: this error. First ring: errors it is linked with (8). 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 (8)
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).
SMTP: 550-5.7.25 The IP address sending this message does not have a PTR record setup, or the corresponding forward DNS entry does not point to the sending IP
Gmail (and others) require your sending IP to have a reverse DNS (PTR) record that resolves back to the same IP; yours has none o…
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…
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…
SPF: spf=permerror — Multiple SPF records found for example.com
The domain publishes more than one TXT record starting with `v=spf1`; receivers must treat that as a permanent error.
SPF: Received-SPF: softfail (google.com: domain of transitioning bounce@example.com does not designate 203.0.113.5 as permitted sender)
The server that sent the mail is not listed in the sender domain's SPF record, so the receiver marks it fail or softfail.
DMARC: dmarc=none (no DMARC record found for example.com) — bulk sender requirements not met
The sender's domain publishes no `_dmarc` TXT record, so receivers cannot apply any policy; Gmail and Yahoo now require one for b…
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…
Two steps away (15)
PHP mail() returns false / emails not delivered
PHP’s mail() function failed or emails never arrive (spam or rejected).
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…
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.
cURL error 6: Could not resolve host: api.example.com
PHP cURL couldn’t resolve the hostname via DNS.
sudo: unable to resolve host <hostname>: Name or service not known
The machine’s hostname isn’t in /etc/hosts (or DNS), so sudo prints this warning — usually after changing the hostname.
ping: google.com: Temporary failure in name resolution
The Linux host can’t resolve domain names — no working DNS server is configured or reachable.
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: 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…
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.
SMTP: 550 5.1.2 Domain not found / 554 5.4.4 Unable to resolve MX / Host or domain name not found
Mail cannot be routed because the recipient domain has no MX (or A) record, or DNS for it fails.
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.
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.
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…
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…
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