Using the VPS v2 Virtual Server e-mail system, you can create e-mail
aliases, (forwarding addresses). An alias forwards all incoming mail to one or
more specific e-mail addresses, to one or more pre-determined recipients.
Aliases are used to create handy replacements for
difficult-to-remember or long addresses. Aliases can also be used to establish
a set of generic addresses such as webmaster@your_company.com or
info@your_company.com. Establishing a set of aliases like the following
promotes an image of professionalism (even if each alias points to the same
recipient):
-
sales@your_company.com
-
service@your_company.com
-
jobs@your_company.com
Since a single alias can point to multiple recipients,
aliases can be used to create simple mailing lists or announcement boards that
point to appropriate sets of individuals, allowing the alias address to be used
as a "broadcast" address for the group:
-
everyone@your_company.com
-
marketing@your_company.com
-
engineering@your_company.com
If you have a large alias file, add comments to avoid
confusion. Any lines that begin with the # character are considered a comment
and are ignored.
To create an alias, add the alias to the /etc/mail/aliases
file and type make to generate the aliases.db file.
Creating an Alias for a Local User
To create an alias for a local user:
-
Go to /etc/mail.
-
Invoke an editor for the /etc/mail/aliases
file and add the following line, replacing “alias” with the alias name, and
“recipient” with a simple user name.
-
alias: recipient
For example:
webmaster: ted
Type newaliases to rebuild the
access database only.
Creating an Alias for an Off-Site Recipient
To create an alias for an off site recipient:
-
Go to /etc/mail.
-
Invoke an editor for the /etc/mail/aliases
file and add the following line, replacing “alias” with the alias name, and
“recipient” with a full e-mail address.
alias: recipient
For example:
sales: tony@hotshotmail.com
-
Type newaliases to rebuild the
access database only.
Note: Do not worry about
multiple aliases, or one alias actually pointing to another alias. Sendmail
performs multiple lookups to determine the recipient.
You should begin each alias at the start of the line,
because lines begin each alias at the start of the line; lines that begin with
a space or tab are considered continuation lines. The colon separating the
alias and the recipient must be on the same line as the alias, and it may be
preceded or followed by spaces or tabs.
Creating a Mailing List
Using the /etc/mail/aliases
file, you can create mailing lists that include many recipients. Mailing lists
save time. You can either create a simple mailing list, or you can create a
more sophisticated mailing list that you are able to edit independently of the
alias file.
The :include:
statement causes the contents of a separate file to be read in, or included, in
the aliases file. This allows the recipient
list to be stored in an outside file where it can be manipulated independently
of the aliases file.
Edit the /etc/mail/aliases
file by typing in the form of:
alias: recipient1, recipient2, recipient3, recipient4,...
Creating a Mailing List with :include:
To create a mailing list using the include statement:
-
Go to /etc/mail.
-
Edit the /etc/mail/aliases file by
typing in the form of:
alias: :include:/pathname
The /pathname is
the virtual pathname of the file. For example:
subscribers: :include:/etc/subscribers.list
-
Type newaliases to rebuild the
access database only.
The file referenced by include is a text file containing a
list of recipient addresses. Each line is a list of one or more recipient
addresses. Multiple addresses appearing on a line should be separated by
commas. Like the /etc/mail/aliases file,
any line that begins with a # character is considered a comment and is ignored,
as are blank lines.
For more information about software that enables you to
create automated mailing lists, see Majordomo (http://www.majordomo.com). Majordomo works
with the /etc/mail/aliases file. It automates
address addition and removal of recipients of the mailing list through the use
of the :include: statement.
Virtmaps
Virtmaps, or e-mail address mappings are similar to
aliases but are tailored to virtual host domain names. VPS v2 Virtual Servers that have one or
more domain names associated with them in addition to their primary domain name
use virtmaps to organize their aliases.
Aliases do not incorporate information about the hostname
portion of an e-mail address, just the username portion. As a result, conflicts
occur when two virtual domains have e-mail addresses with identical usernames,
such as "webmaster". Virtual e-mail address mappings are designed to
avoid these conflicts by ensuring that mail sent to
"webmaster@domain1.com" and mail sent to "webmaster@domain2.com"
do not collide, even though both domain names ("domain1.com" and
"domain2.com") are associated with the same VPS v2 Virtual Server.
Creating a Virtmap
The first time you create a virtmap, you must create a virtusertable
file that generates the virtusertable.db.
-
Go to /etc/mail.
-
Invoke an editor and name the file virtusertable.
%vi virtusertable
-
Type the following:
address recipient
where “address” is replaced with the full address you
would like to route to and “recipient” is replaced with the recipient address.
The actual virtusertable.sample file provides these examples:
username@a.sample.hostname localuser
username@a.sample.hostname specificuser@a.possibly.different.hostname
@another.sample.hostname specificuser@a.possibly.different.hostname
@yet.another.sample.hostname
%1@a.possibly.different.hostname
-
Types make to rebuild the
database. Likewise, make will generate a
new sendmail.cf file if there are changes
to the sendmail.mc file, and then it will
restart Sendmail.
or
Type makemap hash /etc/mail/virtusertable < /etc/mail/virtusertable
to rebuild the access database only.
-
Add the source hostname to /etc/mail/local-host-names so that Sendmail
will accept mail for the source hostname. If the domain was added to your
account through ordering, the domain should already be
in this file.
% cd /etc/mail/
% vi local-host-names
Note: You must include
the @ symbol in front of any domain, if you do not specify the entire e-mail
address.
Sample of grouped virtmaps
In the following sample the address mappings are grouped
together by domain name. The first address mapping in the "abc.com"
group is redirecting mail to a non-local user. The second address mapping is
directing mail to a local user.
#abc.com mappings
bob@abc.com bob@aol.com
webmaster@abc.com carol
#xyz.com mappings
bob@xyz.com bob
webmaster@xyz.com john
Note: Unlike the /etc/mail/aliases file, there is no colon
character between the address and the recipient in the /etc/mail/virtusertable
file.
Using a Catchall
A wildcard address mapping serves as a “catchall” that
matches any address at a hostname that is not already explicitly listed.
-
Go to /etc/mail.
-
Invoke an editor for the virtusertable file.
% vi virtusertable
-
Type the following:
@hostname recipient
where hostname is replaced with
the hostname you want to create the wildcard for, and recipient is replaced
with the recipient’s address.
-
Save the file and close the editor.
-
Types make to rebuild the
database. Likewise, make will generate a
new sendmail.cf file if there are changes
to the sendmail.mc file, and then it will
restart Sendmail.
or
Type makemap hash /etc/mail/virtusertable < /etc/mail/virtusertable
to rebuild the access database only.
The following is a sample virtusertable file with
catchalls:
#abc.com mappings
bob@abc.com bob@aol.com
webmaster@abc.com carol
@abc.com carol
#xyz.com mappings
bob@xyz.com bob
webmaster@xyz.com john
@xyz.com bob
Note: Always place
catchalls at the end of a hostname section in the /etc/mail/virtusertable
file to emphasize their nature as a default recipient (if none of the previous
mappings match).
Forwarding root’s mail to the Administrative User
For security reasons, the user root has no mail
privileges. Instead, messages for root are configured by default in the aliases
file, to be delivered to the Administrative User.
If you create a catchall, the alias entry for the
Administrative user to receive e-mail for the root user will no longer work.
Instead, e-mail for the root user will be delivered to the owner of the catchall.
To solve this problem, you must create a virtmap for entry for each domain,
including the primary and subhosted domains, with root@domain.name as the
e-mail address and the Administrative user as the recipient.
The following is an example of how this should look in the
virtusertable:
root@abc.com admin
root@xzy.com admin
@abc.com carol
@xyz.com bob
Combining Virtmaps and Aliases
This is the order in which incoming mail is read as it is
routed:
Virtmaps > Aliases > Users > Bounce
When a piece of new mail arrives, address mappings are
processed first before aliases are checked. After the address mapping process
is complete and a local recipient has been determined, the aliases database is
checked next to see if the recipient exists as an alias. If so, the message is
routed to the target of the alias. If not, the recipient must exist as a local
username, and a delivery attempt is made to place the message in that incoming
mailbox.
Differences between Virtmaps and Aliases
Perhaps the most important difference between virtmaps and
aliases is that Sendmail performs repeated lookups in /etc/mail/aliases until
it completely resolves the recipient address, but performs only one database
lookup in /etc/mail/virtusertable file when handling virtmaps.
The right-hand portion of an /etc/mail/virtusertable line
should consist solely of a recipient address and must not contain any of the
more advanced features. Items such as :include: statements, delivery to a file
(signaled by a / character), or delivery to a program (signaled by a |
character) may not be used in virtusertable.
The right-hand portion of a /etc/mail/virtusertable line
(the recipient portion) must not depend on the left-hand portion (the address
portion) of any other line.
Unlike the aliases file, multiple recipients must not be
listed in a single address mapping.
Virtmaps Summarized
If you have only one domain (the primary domain) pointing to your
VPS v2 Virtual Server, then use of virtusertable is not necessary.
-
Virtmaps are stored in /etc/mail/virtusertable.
-
After adding an entry to the virtusertable, rebuild the database
using the make command.
-
Type address maps like the following example:
address recipient
For example:
webmaster@abc.com john
-
Do not include colons in address maps and include only one user
on the right side. If multiple recipients are needed on the right, then specify
the name of an alias on the right hand side, and then create the alias in
/etc/mail/aliases with the multiple recipients.
-
The catchall for a domain should be listed last.
Blocking E-mail from Specific Hosts (Spammers)
To block e-mail from spammers:
-
Go to /etc/mail.
-
Edit the /etc/mail/access file,
using your preferred editor.
% pico access.db
-
Type the following:
username@hostname REJECT
or
hostname REJECT
12.34.56.78 REJECT
12.34.56.79 REJECT
or
12.34 REJECT
where “username” is the username of the sender, and
“hostname” is the hostname portion of the sender's address, 12.34.56.78 is the
IP address of the sender, and 12.34 is the IP block of the sender.
-
Save the file and close the editor.
-
Types make to rebuild the
database. Likewise, make will generate a
new sendmail.cf file if there are changes
to the sendmail.mc file, and then it will
restart Sendmail.
or
Type makemap hash /etc/mail/access < /etc/mail/access
to rebuild the access database only.
Maintaining the E-mail Log File
Your e-mail log files are in /var/log/maillog.
For information on tools to use in maintaining your e-mail log file, see Chapter 9.
Important Commands, Directories, and Files
The following table describes commands, directories, and
files used to manage the e-mail server.
Name |
Type |
Description |
cd /etc/mail make |
command |
Rebuilds the aliases, access, and virtusertable files. It
is not necessary to restart Sendmail after running this command. |
cd /etc/mail make restart |
command |
Restarts the current Sendmail processes. |
cd /etc/mail
make stop |
command |
Stops the current Sendmail processes. |
cd /etc/mail make start |
command |
Starts Sendmail. |
restart_send
mail |
command |
Restarts both Sendmail daemons (accepting connections and queuerunner)
and also restarts the SMTP authentication daemon, saslauthd. |
/etc/mail/
access |
file |
Lists mail addresses or domains the server is to refuse
message from. |
/etc/mail/
aliases |
file |
Lists aliases |
/var/log/
maillog |
file |
Contains log of e-mail messages |
/etc/mail/
sendmail.cf |
file |
The Sendmail main configuration file |
/etc/mail/
virtusertable |
file |
Lists virtmaps and catchalls |
Order of Mail Delivery: virtmaps > aliases >
users > bounce |
For More Information
For more information about the topics discussed in this
chapter, Visit our Technical Support Pages
http://www.sendmail.org
|
