Macintosh clients unable to send mail through WorldMail

RFC 821 states all mail clients must send a valid HELO command during the beginning of an SMTP transaction.

A valid HELO command is comprised of a domain name or a host.domain name. However, Macintosh determines its hostname by performing a reverse DNS lookup of the IP address configured in the TCP/IP Control Panel. If you're on a small LAN, you probably do not have domain name services running.

When the client sends the HELO command or EHLO (Extended SMTP), it sends the IP address since it does not have a valid hostname to send. This is invalid.

To allow this, you need to edit a registry setting HKEY_LOCAL_MACHINE/ISOCOR/SERVICES/SMTP/LOCALDOMAINS and look for (or add) a new Dword value AllowEmptyHelo and set the value data to 1.

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KEYWORDS: ALLCARDS, WM, MACINTOSH, SEND