SMTP Connector setting in Exchange 2003

Quick question.  I want to add a smart host to a new SMTP Connector that I created.  Which of the three option will allow for the fastest delivery to the smart host?  

1. Enter full fqdn of smart host.  (E.g.  mail.abc.com; This dns name has multiple A records)
2. Enter the fqdn of each hosts separately in the smart host field.  (E.g. mx1.abc.com,mx2.abc.com)
3. Enter the IP address of each hosts separately in the smart host field. (E.g. [123.123.123.123][132.132.132.132])

Thanks!
e90mdreiAsked:
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AJermoConnect With a Mentor Commented:
Best practice is a relateive term.
The advantage to using the FQDN is if the IP address changes but is updated in DNS no further confiiguration is required.  FQDN is more readable to figure out what it is if you use descriptive names.
The disadvantage is when the DNS cache expires the system will re-lookup the records. Every time the system uses the smart host it will ask for the lookup but the OS will have it cached. This increases the overhead slightly.

The advantage to using IP is no further lookup or operation is required.
Disadvantage is if the smarthost IP changes the configuration on the connector will require updating.

As yourself a question...how often do IPs on servers/gateways change? ... most likely the answer is "not often enough to matter".
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AJermoCommented:
IP address is always faster because the system never has to do a dns lookup.
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AJermoCommented:
seperate each ip with semi-colon.
[10.10.10.10];[20.20.20.20]

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e90mdreiAuthor Commented:
ok, so the multiple IP in the smart host field is best practices?  Rather than a dns record with multiple A records?  
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AJermoCommented:
The solution you're suggesting with a single dns name with multiple A records will also work as long as round robin is enabled on the configured DNS server.
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e90mdreiAuthor Commented:
Ok, I've setup the outbound smtp connector and added the appropriate smart hosts info and added two front-end servers as the bridgeheads.  

Once messages are being sent and is in the smtp connector, is there a delay in forwarding the mail to the smart hosts?  It seems as though the messages in the state of "queue" from 3-10 mins.  ??  

This smtp connector has the lowest cost therefore has priority over other connectors.  Also, I'm trying out the dns name of the smarthost first to try.  

Please advise..
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