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502

Command Not Implemented

The server recognizes the command but hasn't implemented it. This may indicate feature incompatibility.

What does this error mean?

SMTP error 502 indicates the server knows the command but doesn't support it:

  • SMTP extension not supported by the server
  • Feature intentionally disabled by administrator
  • Legacy server with limited command support
  • Security policy blocking certain commands

Common Causes

  • extension_off
    Unsupported Extension

    Your mail server is using an SMTP extension that the recipient's server doesn't support.

  • history
    Legacy Server

    The receiving server is running older software with limited command support.

  • admin_panel_settings
    Disabled Feature

    The feature has been intentionally disabled by the server administrator.

    • How to Fix

    1. Disable Optional Extensions

    Configure your mail server to not require optional SMTP extensions when connecting to this server.

    2. Use Standard SMTP

    Ensure your mail server is using standard SMTP commands that are universally supported.

    3. Contact Administrator

    Contact your mail server administrator to adjust SMTP settings for compatibility.

    Example response 
    502 5.5.1 Command not implemented
502 VRFY command is disabled
502 Command not supported

    Related SMTP Errors

    500 Syntax Error 504 Parameter Not Implemented 503 Bad Sequence of Commands 501 Syntax Error in Parameters

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