421 2.5.2 - A mail transaction protocol command was issued which could not be interpreted, either because the syntax was wrong or the command is unrecognized. This is useful only as a permanent error.

Lookup for "421 2.5.2"

This status code indicates a successful delivery or other operation. Any details are simply notes.

Basic Status Code Details (421)

Service not available, closing transmission channel [This may be a reply to any command if the service knows it must shut down]

Enhanced Status Code Details (2.5.2)

Syntax error

A mail transaction protocol command was issued which could not be interpreted, either because the syntax was wrong or the command is unrecognized. This is useful only as a permanent error.

SMTP Error Code: 421 2.5.2

Lookup for "421 2.5.2"

Basic Status Code Details (421)

Enhanced Status Code Details (2.5.2)

Syntax error