• The Domino 6 router sends, routes, and delivers MIME messages over both SMTP and Notes RPC
• The Domino 6 database format stores MIME messages natively
• Notes 6 clients can create, read, and send MIME messages over both SMTP and Notes RPC

• Leave the Domino 4.6 MTAs in place until the rest of your system is upgraded
• Replace the Domino 4.6 MTAs with Domino 6 mail servers before upgrading the rest of your system
• Rework your messaging infrastructure to eliminating the need for separate SMTP servers because all Domino 6 servers can route Internet mail
• Use a mixed strategy

Leave your Domino 4.6 MTA servers in place

This scenario leaves your Domino 4.6 MTA servers in place until you have upgraded all other Domino servers and Notes clients to Lotus Notes/Domino 6. This option ensures a known level of functionality for Internet message traffic during the upgrade process, but does not allow your organization to use the new Internet mail features of the Domino 6 server. For example, Notes 6 clients cannot send native MIME to Internet recipients with this strategy -- their Domino 6 mail server must convert the native MIME to Notes format and then transfer it to the Domino 4.6 MTA. This increases load on the mail server and could cause some loss of message fidelity.

Replace all Domino 4.6 MTAs with Domino 6 mail servers first

The Domino 6 mail servers perform the same tasks as Domino 4.6 MTAs, with greater performance, stability, and message fidelity. Your organization can use Domino 6 features such as restrictions to prevent spamming and control maximum message size. Notes 6 and Internet clients can use native MIME seamlessly.

If you upgrade your Domino 4.6 MTA servers to Lotus Domino 6 before upgrading the rest of your Domino system, the Domino 6 mail servers store MIME messages in MIME format, but must convert the messages to Notes format, to an attachment containing the MIME message, or to both a Notes format message and an attachment, when transferring the message to a Domino 4.6 server.

For more information, see the topic Internet mail routing in mixed-release environments.

As you change your infrastructure to Lotus Domino 6, the Domino 6 mail servers can route MIME messages to other Domino 6 mail servers, which can deliver the messages or perform the conversion for Domino 4.6 servers.

Replace all Domino 4.6 MTAs with Domino 6 mail servers during system upgrade

This strategy is similar to upgrading MTAs before upgrading the rest of your system, but allows you to select when to begin conversion on hub servers or spoke servers. For example, if you use a Domino POP3 server to host mail for a large number of POP3 clients, you might wait to upgrade your MTAs until you upgrade the POP3 server to prevent any need for conversion by the POP3 server or its hub. In addition, if your hub servers are near capacity, but your spoke servers have extra capacity, you might wait to upgrade the MTA servers until the spoke servers have been upgraded to prevent placing the conversion load on the hubs.

Rework the messaging infrastructure to implement a distributed infrastructure

In a Domino 4.6-style Internet messaging infrastructure, all Internet mail messages route through one or more dedicated MTA servers. In Lotus Domino 6, dedicated MTA servers are no longer necessary as all Domino 6 servers can route Internet mail, including performing any necessary conversions. If you want to move from a Domino 4.6 "gateway" architecture to a more distributed Internet mail routing infrastructure, note the following issues:

• When you enable a distributed infrastructure, where messages no longer route through a few SMTP servers, but rather use the Domino 6 router to transfer Internet mail, consider the possible conversion load from Notes clients. If a Notes client sends a message to Internet recipients in Notes message format, the Domino 6 mail server converts that message to MIME and routes it. If your mail servers are near capacity, this conversion load may place an unacceptable strain on them. However, spreading conversion across all mail servers, instead of concentrating it on a few MTA servers, is often a performance improvement for organizations. Depending on your system, you may want to wait until you begin converting Notes clients to Lotus Notes 6 to rework your messaging architecture. Because Notes 6 clients can send and read MIME, the conversion load on the mail servers is less.
• Enabling SMTP routing on all mail servers in your organization does not require the mail servers to have direct Internet access. You can use a relay host for mail routing beyond your local Internet domain and for security purposes. The relay host can be a Domino 6 mail server, a Domino 4.6 MTA, or a third-party product.
• If you enable direct Internet access for all mail servers, make sure they are correctly configured and properly registered with the InterNIC. For security reasons, many systems do not accept connections or mail from servers that are improperly configured or not registered.

Some organizations will use a combined strategy depending on their needs and infrastructure. For example, a multinational organization may immediately upgrade its MTA servers in one part of the world and wait until the Domino system is at Lotus Domino 6 to upgrade in another. Use these scenarios and the needs of your organization to determine the optimal upgrade strategy.

See Also

How Lotus Domino 6 replaces the Domino 4.6 MTA
Replacing Domino 4.6 MTAs with Domino 6 mail servers