How to read SMTP errors
4xx codes are usually temporary: the server may retry delivery. 5xx codes are usually permanent: address, DNS, SPF, DKIM, DMARC, SMTP authentication, message content or sender reputation may need correction. If customer mail has errors, Hostilla.pl support can help check logs and configuration. Affordable good mail hosting means e-mail moving, PHP-FPM, OPcache, Redis or Memcached for applications, backup, security, price in PLN and renewal for the next year.
Primary SMTP 4xx/5xx replies
SMTP 421 Service not availableerror meaning, causes and mail diagnosticsSMTP 450 Mailbox unavailableerror meaning, causes and mail diagnosticsSMTP 451 Local error in processingerror meaning, causes and mail diagnosticsSMTP 452 Insufficient system storageerror meaning, causes and mail diagnosticsSMTP 455 Unable to accommodate parameterserror meaning, causes and mail diagnosticsSMTP 500 Syntax errorerror meaning, causes and mail diagnosticsSMTP 501 Syntax error in parameterserror meaning, causes and mail diagnosticsSMTP 502 Command not implementederror meaning, causes and mail diagnosticsSMTP 503 Bad sequence of commandserror meaning, causes and mail diagnosticsSMTP 504 Command parameter not implementederror meaning, causes and mail diagnosticsSMTP 521 Server does not accept mailerror meaning, causes and mail diagnosticsSMTP 530 Authentication requirederror meaning, causes and mail diagnosticsSMTP 534 Authentication mechanism too weakerror meaning, causes and mail diagnosticsSMTP 535 Authentication credentials invaliderror meaning, causes and mail diagnosticsSMTP 538 Encryption requirederror meaning, causes and mail diagnosticsSMTP 550 Mailbox unavailableerror meaning, causes and mail diagnosticsSMTP 551 User not localerror meaning, causes and mail diagnosticsSMTP 552 Exceeded storage allocationerror meaning, causes and mail diagnosticsSMTP 553 Mailbox name not allowederror meaning, causes and mail diagnosticsSMTP 554 Transaction failederror meaning, causes and mail diagnosticsSMTP 555 MAIL FROM/RCPT TO parameter not recognizederror meaning, causes and mail diagnosticsSMTP 556 Domain does not accept mailerror meaning, causes and mail diagnostics
Enhanced SMTP status codes
SMTP 4.0.0 Temporary delivery failureerror meaning, causes and mail diagnosticsSMTP 4.2.0 Mailbox temporarily unavailableerror meaning, causes and mail diagnosticsSMTP 4.2.2 Mailbox full temporarilyerror meaning, causes and mail diagnosticsSMTP 4.3.0 Mail system problemerror meaning, causes and mail diagnosticsSMTP 4.4.1 No answer from hosterror meaning, causes and mail diagnosticsSMTP 4.4.2 Bad connectionerror meaning, causes and mail diagnosticsSMTP 4.4.4 Unable to routeerror meaning, causes and mail diagnosticsSMTP 4.7.0 Temporary security policyerror meaning, causes and mail diagnosticsSMTP 4.7.1 Temporary policy rejectionerror meaning, causes and mail diagnosticsSMTP 5.0.0 Permanent delivery failureerror meaning, causes and mail diagnosticsSMTP 5.1.0 Bad destination addresserror meaning, causes and mail diagnosticsSMTP 5.1.1 Bad destination mailbox addresserror meaning, causes and mail diagnosticsSMTP 5.1.2 Bad destination system addresserror meaning, causes and mail diagnosticsSMTP 5.2.2 Mailbox fullerror meaning, causes and mail diagnosticsSMTP 5.3.0 Mail system errorerror meaning, causes and mail diagnosticsSMTP 5.4.1 No answer from hosterror meaning, causes and mail diagnosticsSMTP 5.4.4 Unable to routeerror meaning, causes and mail diagnosticsSMTP 5.6.0 Media or content errorerror meaning, causes and mail diagnosticsSMTP 5.7.0 Security or policy statuserror meaning, causes and mail diagnosticsSMTP 5.7.1 Delivery not authorizederror meaning, causes and mail diagnosticsSMTP 5.7.8 Authentication credentials invaliderror meaning, causes and mail diagnostics