Error map
554 5.7.1 Message rejected as spam SMTP: 554 5.7.1 Message content rejected / Your message looks like spam (spam score exceeded)
Email / SMTP · layer 2, Network
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.
Directly related (7)
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: 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: 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: 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: 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: 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.
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 (19)
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.
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: 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.
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.
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: 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.
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: 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…
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: 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…
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: 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…
SPF: spf=permerror — Too many DNS lookups (limit is 10)
Your SPF record needs more than 10 DNS lookups to evaluate, so receivers treat SPF as a permanent error and the check fails.
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.
Map another error
Popular: 500403400ORA-009331064Critical errorFileNotFoundException assemblyTypeError