The User Database (userdb) allows recipient addresses to be changed so that they can be delivered to new hosts. For example, [email protected] can be transformed with the User Database into [email protected]. The genericstable provides the same type of transformation on the sender's address.

To begin, create a file of the form:

user                [email protected]
[email protected]    [email protected]

In it, each line begins with the old address, either the user part alone, or the full address. On the right is the new address for that sender. One example of a use for this table might be to make the user news always appear as though it was from the news machine:

news            [email protected]
[email protected] [email protected]

Note that the bare user part (news in the first line) is looked up only if sendmail considers it to be in the local domain. If a domain is listed (as in the second line in the preceding example) that entry is looked up only if it is in a special class defined with the GENERICS_DOMAIN mc macro (Section 4.8.1). If you want subdomains to also match, you must declare the generics_entire_domain feature (FEATURE(generics_entire_domain)). Ways to list domains in that special class are outlined later in this chapter.

The makemap(1) program (Section 5.5) is then used to convert this file into a database:

makemap hash db_file <  text_file  

Here, db_file is the name you give to the created database, and text_file is the name of the source text file.

Note that local and nonlocal hosts can appear in the special class defined with the GENERICS_DOMAIN mc macro. Also note that the members of $=w are not automatically placed into this special class.

The genericstable feature enables this lookup by including a K configuration command:

Kgenerics hash /etc/mail/genericstable

The form of the genericstable feature's declaration is:

FEATURE(`genericstable')

The genericstable feature is one of those that can take an argument to specify a different form of, or a different name for, the database:

FEATURE(`genericstable',`dbm -o /etc/mail/genericstable')

The extra argument causes the earlier K command to be replaced with the following one:

Kgenerics dbm -o /etc/mail/genericstable

See -o for a description of the K command -o switch.

You can also provide an extra argument that is a literal LDAP:

FEATURE(`domaintable', `LDAP')

The default in this instance becomes the following (we have wrapped the lines to fit the page):

Kgenerics ldap -1 -v sendmailMTAMapValue -k (&(objectClass=sendmailMTAMapObject)
(|(sendmailMTACluster=${sendmailMTACluster})(sendmailMTAHost=$j))
(sendmailMTAMapName=generics)(sendmailMTAKey=%0))

See ldap (was ldapx) for a description of the ldap database type and its -1, -v, and -k switches.

The genericstable should be enabled only if you intend to use it. It causes every sender to be looked up in that database.

GENERICS_DOMAIN mc macro

Beginning with V8.8 sendmail, a new mc macro was introduced to make it easier to list domains for use with the genericstable feature. Called GENERICS_DOMAIN, it is used like this:

GENERICS_DOMAIN(`domain1 domain2 etc.')

Each domain that you intend to list should be listed individually and separated from the others by spaces. Multiple GENERICS_DOMAIN lists can be declared in your mc file:

GENERICS_DOMAIN(`domain1')
GENERICS_DOMAIN(`domain2')
GENERICS_DOMAIN(`etc.')

If you are currently declaring the $=G class directly under the LOCAL_CONFIG mc macro, you are encouraged to convert to this new mc macro. Use of it will insulate you from change in the future if a different sendmail class is ever used.

GENERICS_DOMAIN_FILE mc macro

Beginning with V8.8 sendmail, a new mc macro was introduced to make it easier to list domains with the genericstable feature. Called GENERICS_DOMAIN_FILE, it is used like this:

GENERICS_DOMAIN_FILE(`/etc/mail/genericdomains')

This declaration causes the list of domains to be read from the file /etc/mail/genericdomains. Because GENERICS_DOMAIN_FILE is implemented with an F configuration command (Section 22.1.2), you can add whatever F command arguments you desire. For example:

GENERICS_DOMAIN_FILE(`-o /etc/mail/genericdomains')

Here, the -o switch makes the presence of the /etc/mail/genericdomains file optional.

If you are currently reading a list of domains from a file declared with an FG configuration command, you are encouraged to convert to this new macro. Use of it will insulate you from change in the future if a different class is ever used.