SpamAssassin Rule: RCVD_NUMERIC_HELO

Standard description: Received: contains an IP address used for HELO


In an SMTP session the argument to the first command a client sends (EHLO or HELO) should be the client identifier. RFC2821 specifies the fully-qualified domain name of the SMTP client, the older standard RFC821 refers to the host name.

In situations that the client does not have a meaningful domain name the client SHOULD send an address literal (an IP address enclosed by square brackets).

If a Received: header is parsed that indicates the EHLO/HELO identifier was given as an IP address, but not enclosed by square brackets, this is in violation of the RFC.

Further Info

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