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 Virtual Server.

1. From your Virtual Server ~/etc/virtmaps file, type:

   address recipient

   where address is replaced with the full address you would like to route to and recipient is replaced with the recipient address.

2. From the command-prompt, enter vnewvirtmaps. This action recreates the ~/etc/virtmaps.db file so the changes take effect.

#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/aliases file, there is no colon character between the address and the recipient in the ~/etc/virtmaps file.

Using Wildcard Mappings
A wildcard address mapping serves as a "catch-all" that matches any address at a hostname that is not already explicitly listed.

Creating Wildcard Mappings

1. From your Virtual Server ~/etc/virtmaps file, type:

   hostname recipient

   where hostname is replaced with the hostname you want to create the wildcard for and recipient is replaced with the recipient address.

2. From the command-prompt, enter vnewvirtmaps. This action recreates the ~/etc/virtmaps.db file so the changes take effect.

#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: You can place wildcard mappings anywhere in the ~/etc/virtmaps file. However, you should place them at the end of the section, so that you emphasize their nature as a default recipient (if none of the previous mappings match).

Combining Mappings and Aliases
When a piece of new mail arrives, address mappings are processed first, before aliases are checked. Once 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 his or her incoming mailbox.

Differences Between virtmaps and aliases
One difference between the ~/etc/virtmaps and ~/etc/aliases files is that multiple recipients must not be listed in a single address mapping.

A related difference lies in the fact that the right-hand portion of an ~/etc/virtmaps 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 the virtmaps file.

Perhaps the most important difference between virtmaps and aliases is that sendmail performs only a single database lookup in the ~/etc/virtmaps.db file when handling address mappings. The net effect of this is that the right-hand portion of an ~/etc/virtmaps line (the recipient portion) must not depend on the left-hand portion (the address portion) of any other line. The sendmail program does not lookup further mappings to trace recipient addresses (unlike alias processing where sendmail performs repeated alias lookups until it completely resolves the recipient address).

1. If you have only one domain pointing to your Virtual Server, then use of the virtmaps file is not necessary.
2. Address maps are stored in the ~/etc/virtmaps file.
3. After adding an address map to the virtmaps file, regenerate the virtmaps.db file with the vnewvirtmaps command.
4. Address maps follow a simple format:

   address            recipient

   For example:
   webmaster@abc.com      john

5. No colons in address maps and 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 the aliases file with the multiple recipients.
6. The catch-all for a domain should be last.