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The Aliases Database Map and .forward Files

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E0802 Edition 6 ♥
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The aliases database map /etc/mail/aliases describes user ID aliases used by Sendmail and is formatted as a series of lines of the form

name: addr_1, addr_2, addr_3, . . .

The name is the name to alias, and the addr_n are the aliases for that name. addr_n can be another alias, a local username, a local filename, a command, an include file, or an external e-mail address.

Local Username
username

The username must be available via getpwnam(3). Note that names specified here will be subject to recursive alias lookups; to suppress further alias lookups against this name, prefix the name with a backslash (\) character. MPE usernames have the format USER.ACCOUNT.

Local Filename

/path/name

Messages are appended to the file specified by the full absolute pathname (starting with a slash (/))

Command

|command

A command starts with a pipe symbol (|), it receives messages via standard input. To execute a command with parameters, enclose the entire expression in quotes, i.e., "|command parm1 parm2 parm3".

Include File
:include: /path/name

The aliases in pathname are added to the aliases for name.

External E-Mail Address
user@domain

An e-mail address in RFC 822 format.

Lines beginning with white space are continuation lines. Another way to continue lines is by placing a backslash directly before a newline. Lines beginning with # are comments.

Aliasing occurs only on local names. Loops cannot occur, since no message will be sent to any person more than once.

After aliasing has been done, local and valid recipients who have a ".forward" file in their home directory have messages forwarded to the list of users defined in that file.

This is only the raw data file; the actual aliasing information is placed into a binary format in the file /etc/mail/aliases.db using the program newaliases(1). A newaliases command must be executed each time the aliases file is changed for the change to take effect:

  1. :HELLO SERVER.SENDMAIL

  2. :XEQ SH.HPBIN.SYS -L

  3. shell/iX> newaliases

Each local user can create a .forward file to alter the delivery of their own mail. When delivering mail to local users, Sendmail looks for a file called /ACCOUNT/GROUP/.forward where ACCOUNT is the user's MPE account and GROUP is the user's MPE home group. If this file is found, the contents are parsed as if they were the right-hand side of an aliases file entry. Consider the following example .forward file:

\USER.ACCOUNT, "|/SENDMAIL/CURRENT/bin/vacation USER.ACCOUNT"

This will cause Sendmail to deliver one copy of an email message to the user's normal mailbox (\USER.ACCOUNT), and another copy of an email message will be piped to the Sendmail vacation autoresponder program.

Access_db Feature

The access database map allows you to accept or reject e-mail based on the message envelope and connecting mail server host name. For example:

  1. :HELLO SERVER.SENDMAIL

  2. :XEQ SH.HPBIN.SYS -L

  3. shell/iX> /bin/cat - >/etc/mail/access
    imaspammer.com REJECT
    :EOD

  4. shell/iX> makemap hash /etc/mail/access </etc/mail/access

This will reject all e-mail originating from the domain imaspammer.com.

For more information about the access_db feature, please see /SENDMAIL/CURRENT/cf/README.

Domaintable Feature

The domaintable database map is used to rewrite domain names in e-mail headers. You might find this useful if your company was acquired by a different company and you were forced to change your email domain names. For example:

  1. :HELLO SERVER.SENDMAIL

  2. :XEQ SH.HPBIN.SYS -L

  3. shell/iX> /bin/cat - >/etc/mail/domaintable
    oldcompany.com newcompany.com
    :EOD

  4. shell/iX> makemap hash /etc/mail/domaintable </etc/mail/domaintable

All occurrences of oldcompany.com in e-mail headers would be rewritten to newcompany.com.

For more information about the domaintable feature, please see /SENDMAIL/CURRENT/cf/README.

Genericstable Feature

The genericstable database map is used to rewrite both the user and domain portions of e-mail addresses in outgoing e-mail headers. For example:

  1. :HELLO SERVER.SENDMAIL

  2. :XEQ SH.HPBIN.SYS -L

  3. shell/iX> /bin/cat - >/etc/mail/genericstable
    USER.ACCOUNT@my.local.host customer_servce@company.com
    :EOD

  4. shell/iX> makemap hash /etc/mail/genericstable </etc/mail/genericstable

All e-mail sent by USER.ACCOUNT on the local host my.local.host would have the sender address(es) rewritten as customer_service@company.com. Note that domains being modified by genericstable must be added to /etc/mail/sendmail.cf class {G}.

For more information about the genericstable feature, please see /SENDMAIL/CURRENT/cf/README.

Mailertable Feature

The mailertable database map is used to override the default mail routing behavior in /etc/mail/sendmail.cf. You might find this useful if you needed to route e-mail for certain domains through specific e-mail relays. For example:

  1. :HELLO SERVER.SENDMAIL

  2. :XEQ SH.HPBIN.SYS -L

  3. shell/iX> /bin/cat - >/etc/mail/mailertable
    .bitnet smtp:relay.bit.net
    :EOD

  4. shell/iX> makemap hash /etc/mail/mailertable </etc/mail/mailertable

All mail addressed to hostnames ending in ".bitnet" would be relayed via the host relay.bit.net.

For more information about the mailertable feature, please see /SENDMAIL/CURRENT/cf/README.

Virtusertable Feature

The virtusertable database map is used to remap incoming e-mail addresses in order to facilitate multiple virtual e-mail domains on the same machine. This is very similar to how aliasing works, except that you can also specify domain names in addition to user names. For example:

  1. :HELLO SERVER.SENDMAIL

  2. :XEQ SH.HPBIN.SYS -L

  3. shell/iX> /bin/cat - >/etc/mail/virtusertable
    info@bar.com INFO.BAR
    info@foo.com INFO.FOO
    :EOD

  4. shell/iX> makemap hash /etc/mail/virtusertable </etc/mail/virtusertable

All e-mail addressed to info@bar.com will be delivered to user INFO.BAR, and all e-mail addressed to info@foo.com will be delivered to user INFO.FOO. Note that all domains used in the map keys must also be present in /etc/mail/local-host-names and that your DNS server(s) have been configured with MX entries that route e-mail for those domains to your local machine.

For more information about the virtusertable feature, please see /SENDMAIL/CURRENT/cf/README.



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