Apple Mac OS X Server (version 10.2.3 or later) - Manual (Page 424)

424 Chapter 9
5 Click Save.
Your SMTP mail service may be unable to do a successful reverse-lookup of a server that
identifies itself in a nonstandard way. Specifically, the SMTP service can determine the server
name in a HELO command that doesn’t deviate too much from standard form.
The SMTP service can determine the server name and do a reverse-lookup from HELO
commands like the following:
helo mail.example.com
helo I am mail.example.com
The SMTP service cannot do a reverse-lookup from HELO commands like the following:
helo I’m mail.example.com
helo I am mail server mail.example.com
helo what a wonderful day it is
The following table explains the results for various configurations of the settings for logging
and rejecting unsuccessful reverse-lookups.
Rejecting Mail From Blacklisted Senders
You can have your mail service check an Open Relay Behavior-modification System (ORBS)
server to see if incoming mail came from a known junk-mail sender. ORBS servers are also
known as black-hole servers.
To reject mail from known junk-mail senders:
1 In Server Settings, click the Internet tab.
2 Click Mail Service and choose Configure Mail Service.
3 Click the Filter tab.
4 Select “Use a server for junk mail rejection” and then type the DNS name of an ORBS server.
5 Click Save.
Log Reject Result
No No Accepts all HELO commands
Yes No Accepts all HELO commands and logs each server whose name doesn’t match
or whose name can’t be determined from the HELO command
Yes Yes Logs and rejects each server whose name doesn’t match or whose name can’t
be determined from the HELO command
Important
Blocking unsolicited mail from blacklisted senders may not be completely
accurate. Sometimes it can prevent valid mail from being received.
LL0395.Book Page 424 Wednesday, November 20, 2002 11:44 AM