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Below is the master configuration that goes with this client setup. XOR does a lot of web hosting and accepts and manages mail for many virtual domains. Our first example, the student machine, managed three virtual domains with LDAP and the genericstable. XOR manages about 1,000 virtual domains with the virtusertable. It uses the genericstable for mapping login names to first.last for outgoing mail. It implements aliases with the standard aliases file, which is 3,000 lines long and contains many mailing lists, some with several thousand recipients (and one with over 100,000). All this on a slightly tired, old SunOS sun4m box.

The aliases file should really be cleaned up, and client aliases separated from employee aliases. All the employee aliases point to an IMAP server, and users use IMAP to access their mail.

Note that the divert statements and comments that are usually present at the beginning of a .mc file are missing. They are only necessary if you use shell-style (#) comments at the beginning of your config file.

This site is running sendmail 8.9.3 and uses some of the old (pre-8.10) constructs for configuration lines. Its mail load has caused many of the performance parameters to be set quite a bit higher than their default values.

VERSIONID('@(#)xor.mc3.0 (trent) 3/29/99')

OSTYPE('sunos4.1')

define('confPRIVACY_FLAGS', 'noexpn,novrfy')

define('confMESSAGE_TIMEOUT','5d/72h')

define('LOCAL_MAILER_PATH', '/usr/bin/mail.local')

dnl ##### increase values for performance and heavy load

define('confMCI_CACHE_SIZE', '16')

define('confMCI_CACHE_TIMEOUT', '10m')

define('confCHECK_ALIASES', 'False')

define('confDOMAIN_NAME', 'xor.com')

define('confMAX_MESSAGE_SIZE', '5000000')

define('confDAEMON_OPTIONS','Port=NNN')

define('confQUEUE_LA', 25)

define('confREFUSE_LA', 30)

FEATURE(always_add_domain)

FEATURE(use_cw_file)

FEATURE(virtusertable)

GENERICS_DOMAIN('xor.com')

FEATURE(genericstable)

FEATURE('masquerade_envelope')

FEATURE('redirect')

FEATURE('access_db', 'hash -o /etc/mail/access')

MAILER(local)

MAILER(smtp)

LOCAL_RULESETS

###### Spam and virus checking rules removed; see page 593

As you can see from the diversity of these examples, there is no single right way to set up your configuration file. sendmail contains many constructs for routing mail and munging headers. To some degree, the ones you choose depend on personal preference or on whatever the person from whom you copied the file did.

19.10 SPAM-RELATED FEATURES IN SENDMAIL

Spam is the jargon word for junk mail, also known as unsolicited commercial email. It has become a serious problem, primarily because the sender (at least in the United States) does not pay by the byte, but rather pays a flat rate for connectivity. Or if they do pay per byte, they send a single message with many thousands of recipients and relay it through another machine. The other machine pays the big per-byte cost and the spammer only pays for one copy. In many countries, end users pay per byte received and get pretty angry at having to pay to receive spam.

Spam seems to be primarily a U.S. problem. The U.S. marketing culture has found a gold mine and continues to exploit it.

ISPs in the United States are starting to feel the effects of spam as their support lines have to deal with more and more instances of spam abuse originating from their customers. One ISP in Colorado with about 150 downstream T1 customers (many of them ISPs) needs a half-time person just to deal with spam complaints.

From the marketing folks’ point of view, spam works well. Response rates are high, costs are low, and delivery is instantaneous. A list of 30 million email addresses only costs about $40.

Many spammers try to appear innocent by suggesting that you answer their email with a message that says “remove” if you want to be removed from their mailing list. Although they may remove you, you have just verified for them that they have a valid, current email address; this fact can land you on other