Adding an Additional Host

Adding an Additional Host

If you want IMail Server to receive mail for a second domain with its own users, you must set up a virtual host for the second domain. For example, if your mail server provides mail service for domain1.com, and you also want it to provide mail service for domain2.com, you must create a virtual host for domain2.com.

There are two types of virtual hosts:

Virtual hosts with IP addresses
Virtual hosts without IP addresses

Note: Whether you use a virtual host with an IP address or without an IP address, you must make DNS entries for your domain(s). See "Setting Up DNS for Multiple Mail Hosts" and your DNS documentation for information on creating these entries.

Virtual Hosts with IP Addresses

This is the recommended way to set up virtual hosts, because all capabilities of regular IMail Server hosts are available to virtual hosts with IP addresses. The only limitations of virtual hosts with IP addresses are:

Each virtual host requires its own unique IP address.
In Windows NT/2000, this requires the extra step of adding an IP address in the Windows NT TCP/IP configuration in the Control Panel (Network applet > Protocols > TCP/IP Protocol > Advanced.)

Note: If you are using Windows NT 3.5.1 or later, you can add up to five IP addresses in the Network applet. If you need to add more than five addresses, refer to the documentation for Windows NT/2000.

Virtual Hosts without IP Addresses

Virtual hosts without IP addresses are easier to set up than those with IP addresses. For more information, see "Configuring a Virtual Host". The IMail Server computer assigns a virtual IP address for the selected domain. You can then use an MX record in your DNS to point the virtual host to the primary host (which has a real IP address). There are several limitations of virtual hosts without IP addresses:

When users log on, they must enter the entire userid@hostname.com string for their user ID, so that IMail Server can tell which virtual host the user is associated with. Some mail clients are not able to connect to the virtual host to read mail. This problem exists because some mail clients either have length restrictions for user IDs, or they clip the user ID at the @ sign. You can configure virtual hosts to use a different character to separate the user ID from the hostname, but then you must tell users to use this character in their logon user IDs (for example, userid#hostname.com). To change the character, see "Special Registry Values".
The Whois and Finger servers do not work for virtual hosts without IP addresses.

Virtual hosts without IP addresses are recommended when you have a shortage of IP addresses, or when you want to forward all mail for a domain to a user at another domain. Here is an example of the latter:

Your primary domain is called abracadabra.com. You want all mail sent to merlin.com to be forwarded to info@abracadabra.com. To accomplish this:

Set up a virtual host without an IP address for merlin.com and do not create any users for merlin.com.
Set up a nobody alias for merlin.com pointing to a user ID on abracadabra.com All mail to any user at merlin.com is sent to the specified user at abracadabra.com (in this case, info@abracadabra.com). For more information, see "Processing Mail to Users that Don't Exist".

Configuring a Virtual Host

(assuming Tools > Use Wizards is cleared):

Select the localhost folder in the left panel.
Click Add Host. The Virtual Host Configuration dialog box appears.

The Local Addresses list box shows all IP addresses set up in the Windows TCP/IP properties and any virtual IP addresses assigned by the IMail Server.

Select the IP address for the virtual host (in the Local Addresses list box) or click Add to assign a new virtual IP address to use for the new mail domain.
For the Official Host Name, enter the name of the mail host.

The name entered is used to address mail to the users on the virtual host. For example, if you enter mail.domain2.com, any users you add to the virtual host will receive mail at user@mail.domain2.com.

In the Aliases text box, specify alternate host names for which the server will accept mail. For example, if your mail host name is mail.domain2.com, you can set an alias of domain2.com so that IMail Server accepts mail addressed to fred@mail.domain2.com and also fred@domain2.com. Multiple aliases are separated by a space. This field is limited to 255 characters.
For the Top Directory Name text box, enter the name of the directory where the directories for users, lists, and Web files for this virtual host will be stored.

In most cases, you will use a different directory for each virtual host. It is possible for virtual hosts to share a directory but then users that have the same names will actually share the same mailbox.

Select the type of user database to use for this host.

Use IMail User Database
Use Local NT User Database
Use External User Database

For a description of these options, see User Registration and Authentication in the IMail Server Getting Started Guide.

Enter the default parameters for mailboxes and messages using the following options. These parameters apply to all users on the virtual host. For detailed information on each option, see "Additional Host Settings".

Default Max Mailbox Size. Default maximum size in bytes (characters) for the total of all mailboxes in a user's account.
Default Max Messages. Default maximum number of messages (the total for all mailboxes) that will be allowed in a user's account.
Single Message Max Size. Default maximum size (in bytes) for a single message sent to the server.

Note: Each virtual host (domain) has an independent Single Message Max Size setting. However, the value configured for the domain bound to the IP address to which SMTP client connects to may override the Single Message Max Size setting configured for the virtual host.
For example, if the host bound to the IP address that the email client connects to for email delivery has a 5 MB max setting and the virtual domain that the client is sending email to has a 10 MB max setting, IMail's SMTP service will not accept a message larger than 5 MB.
IMail Web Messaging, however, accepts messages based solely on the Single Message Max Size setting of the local destination domain.

Maximum User Count. Maximum number of users that can be registered for the host.

Note: The Maximum User Count does not apply to virtual hosts that are based on the Windows NT user database or an external database. Furthermore, the displayed counts of users for hosts that use the NT user database or an external database may not be correct.

Click Save, and then click Exit.

After you have created the virtual host, you must add user mail accounts. For information on creating and modifying user mail accounts, see "Working with User Accounts".

Additional Host Settings

Once the virtual host has been configured, it appears in the left panel. Selecting the virtual host in the left panel, displays the host's General tab in the right panel as shown below.

You can use this tab to alter the settings configured during the creation of the virtual host, and to access additional settings. The following options are available on this tab; the first two are not editable:

Official Host Name. The name that is used to address mail to the users on the mail host.

TCP/IP Address. The real or virtual IP address of the mail host.

Top directory. The name of the directory where the directories for users, lists, and Web files for this host are stored.

Host Aliases. Alternate host names for which the host will accept mail. For example, if the mail host name is mail.domain2.com, you can set an alias of domain2.com so that IMail Server accepts mail addressed to fred@mail.domain2.com and also fred@domain2.com. Multiple aliases are separated by a space.

Note: If the Host Alias name is changed, in order for the change to take effect, stop and restart the SMTPD service.

Default Max Mailbox Size. The default maximum size, in bytes, for the total of all mailboxes in a user's account. If the total size exceeds the maximum, new mail is returned to the sender. Enter zero for an unlimited size.

This value is the default limit used when the Max Mailbox Size value, for a user's account, is set to zero. Changing this value automatically changes the limit for all user accounts, on the host, that have zero for the Max Mailbox Size value. Otherwise, the user's Max Mailbox Size value will override.

Single Message Max Size. The maximum size, in bytes, of a single message, with zero being unlimited. Messages that exceed this size are returned to the sender.

Max Outbound Msg Size. The maximum size, in bytes of an outbound message. Messages larger than this size are bounced.

Full Mailbox Notify%. If a value is entered, users are notified when their mailbox is within a certain percentage of being full. For example, if 80 is entered, users receive an email when their mailbox is 80% full. Users get a maximum of one message a day, for three days.

The email message sent to the user is configurable. The text for this message can be customized by creating a Notify.txt file which should be placed in the top directory of the domain. If there is no Notify.txt file, the notification will contain the following standard text:

"User Host  Your mailbox is nearly full, please remove some messages. If you have any questions, see your system administrator." The two tags will be replaced with the user ID and the domain.

Full Mailbox Notify Address. The address of an additional address where an email is sent when a user's mailbox is almost full. For example, this could be the system administrator's address.

Default Max Messages. The default maximum number of messages (total for all mailboxes) that is allowed in a user's account. If the maximum is exceeded, any new mail is returned to the sender. Enter zero for an unlimited number.

This value is the default limit used when the Max Messages value for the user's account is zero. Changing this value automatically changes the limit for all accounts on the host that have zero for their Max Mailbox Msgs value. Otherwise, the user's Max Mailbox Msgs value overrides the value entered here.

Max Users. The maximum number of users that can be registered for this mail host. Enter zero for an unlimited number. The box next to this setting displays the number of users that exist on the host including the "root" user.

Note: This setting does not apply to virtual domains that use the NT user database. The displayed counts of users for domains that use the NT user database may not be correct.

Disable IM (displayed if Ipswitch Instant Messaging server is installed). This option allows you to disable Ipswitch Instant Messaging for the domain. To use this option, Ipswitch Instant Messaging must be configured to use the IMail database. Instant Messaging can also be disabled for each user on the user's General tab.

Virus Scanning (displayed if IMail AntiVirus is installed). Allows you to enable and disable virus scanning for the current domain.

Sub-mailbox Creation. Allows administrators to specify what to do when a message arrives for a user and is addressed to a sub-mailbox which does not exist. Select one of the following actions:

Create. Creates the sub-mailbox and delivers the message.
Send to Inbox. Does not create the sub-mailbox, instead the message is delivered to the "main" mailbox.
Bounce. Bounces the mail as an invalid user.

In the User Database Type area, select one of the following:

IMail Database
NT Database
External Database

Note: Whether you use a virtual host with an IP address or without an IP address, you must make DNS entries for your domain(s). See "Setting Up DNS for Multiple Mail Hosts" and your DNS documentation for information on creating these entries.

Note: If you are using Windows NT 3.5.1 or later, you can add up to five IP addresses in the Network applet. If you need to add more than five addresses, refer to the documentation for Windows NT/2000.

Note: Each virtual host (domain) has an independent Single Message Max Size setting. However, the value configured for the domain bound to the IP address to which SMTP client connects to may override the Single Message Max Size setting configured for the virtual host. For example, if the host bound to the IP address that the email client connects to for email delivery has a 5 MB max setting and the virtual domain that the client is sending email to has a 10 MB max setting, IMail's SMTP service will not accept a message larger than 5 MB. IMail Web Messaging, however, accepts messages based solely on the Single Message Max Size setting of the local destination domain.

Note: The Maximum User Count does not apply to virtual hosts that are based on the Windows NT user database or an external database. Furthermore, the displayed counts of users for hosts that use the NT user database or an external database may not be correct.

Note: If the Host Alias name is changed, in order for the change to take effect, stop and restart the SMTPD service.

Note: This setting does not apply to virtual domains that use the NT user database. The displayed counts of users for domains that use the NT user database may not be correct.

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