Adding Additional Internet Mail Services

You can add an Internet Mail Service to a site that has an existing service. Only one Internet Mail Service can be installed on a single server.

You should consider adding another Internet Mail Service when:

• Backlogs regularly build up in one of the Internet Mail Service queues.
• A backup computer is required to eliminate any interruption of the mail transfer between the Microsoft Exchange Server site and the other SMTP hosts.

When your site has more than one Internet Mail Service, you should consider the following:

• If the amount of mail to specific domains on the SMTP messaging system can be divided, consider configuring each of the Internet Mail Services to process mail for specific domains only.
• You can assign a cost to the address spaces of each Internet Mail Service. This partially determines Internet Mail Service throughput and can be used to optimize Internet Mail Service performance.
• If incoming and outgoing mail to the SMTP messaging system is balanced, consider configuring one Internet Mail Service to process incoming messages and the other Internet Mail Service to process outgoing messages.

When you add a new Internet Mail Service, you may need to perform one or more of the following tasks:

• Modify the address space of existing Internet Mail Services depending upon the address space you assign to the new Internet Mail Service.
• Change the maximum number of inbound and outbound connections of existing Internet Mail Services depending upon the number of inbound and outbound connections you want to assign to the new Internet Mail Service.
• Change the DNS or Hosts file to reflect the existence of the new Internet Mail Service host.
• Change the MX records in DNS to forward mail to a new Internet Mail Service host if the primary Internet Mail Service is down or too busy.