504
SMTP
504 Parameter Not Implemented
A command parameter is not implemented on this server. The command itself is valid but the specific parameter or extension you used is not supported.
当您看到此代码时
When using SMTP extensions or parameters that the server does not support, such as an unsupported AUTH mechanism or an unrecognized MAIL FROM parameter.
如何修复
Check the server's EHLO response for supported extensions and parameters. Use only the mechanisms and parameters listed in the server's capability advertisement.
与之对比
指南
Debugging SMTP Delivery Failures: 4xx Temporary vs 5xx Permanent
Debugging & Troubleshooting
SMTP Reply Codes: What Your Email Server Is Telling You
Email Delivery
Improving Email Deliverability: SPF, DKIM, and DMARC Setup
Email Delivery
Diagnosing Email Bounces: Soft (4xx) vs Hard (5xx)
Email Delivery
SMTP Authentication Methods Explained
Email Delivery
Email Header Analysis: Tracing Delivery Path
Email Delivery
Bulk Email Delivery: Avoiding the Spam Folder
Email Delivery
DMARC Reporting: Analyzing Aggregate and Forensic Reports
Email Delivery
IP Warming for Email: Building Sender Reputation from Scratch
Email Delivery
Email Feedback Loops (FBL): Processing Spam Complaints
Email Delivery
Transactional Email Best Practices: Receipts, Alerts, and Password Resets
Email Delivery
DNS Record Types Explained: A, AAAA, CNAME, MX, TXT, and Beyond
DNS & Networking
TCP Three-Way Handshake and Connection Lifecycle
DNS & Networking
RFC 5321: SMTP Protocol Deep Dive
Protocol Deep Dives
RFC 959: FTP Protocol Deep Dive
Protocol Deep Dives
TLS 1.3: Faster, Simpler, More Secure
Protocol Deep Dives
术语表
Status Code
Media Type (MIME Type)
TLS Handshake
TLS Certificate (SSL Certificate)
Cipher Suite
Authentication
TCP/IP
Three-Way Handshake
Port Number
Firewall
IPv6
Exponential Backoff
Error Code Mapping
Poison Message
Request-Response Model
RFC (Request for Comments)
IANA (Internet Assigned Numbers Authority)
Message Framing
Connection-Oriented
Text vs Binary Protocol
MX Record
PTR Record
SMTP Relay
SPF, DKIM, and DMARC
Bounce Rate (Email)
Email Deliverability
MTA (Mail Transfer Agent)
SMTP Pipelining
Greylisting
Backscatter
Envelope vs Header
STARTTLS
SMTP Authentication (SMTP AUTH)
Open Relay
Email Queue
MIME Multipart
ARC (Authenticated Received Chain)
BIMI (Brand Indicators for Message Identification)
DSN (Delivery Status Notification)
Email Header Injection
SMTP Enhanced Status Codes
MDN (Message Disposition Notification)
MIME Type
TLS Versions
TLS 1.3
Certificate Authority (CA)
Forward Secrecy (PFS)
SNI (Server Name Indication)
TLS Session Resumption
Key Exchange
PKI (Public Key Infrastructure)