Exchange 2003 Smart Hosts

Hi,

Im reading up on SMTP connectors and im curious as to what method a smart host uses if all mail is to be routed to it for sending mail.

Here is the 2 options in the connector:

(Use DNS to route all outgoing mail through the connector. If you use DNS to route outgoing mail, the SMTP connector uses DNS to resolve the IP address of the remote SMTP server, and then it delivers the mail.

• Specify a smart host (another server to which the connector routes all mail). The smart host takes responsibility for DNS resolution and delivers the mail.)

May seems like a stupid question, but, if i use a smart host, is it just off loading the dns resolution to the smart host and does it take care of reverse lookups for spam?

any insight is greatly appreciated!

Flames1000

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Comments

geekie

im curious as to what method a smart host uses if all mail is to be routed to it for sending mail.

I guess that depends on how the smart host is configured. Basically, a smart host is an SMTP server with the permissions to relay outgoing e-mail messages, from other internal SMTP servers, to the Internet.

Danman32

Yes, a smarthost could offload the DNS, but there can be other reasons for using a smarthost, though offloading DNS resolution would be a fringe benefit.

One benefit is if conditions of the SMTP originator would not allow reception of a message from the originator to the receiver. For example, AOL and various other major ISPs will not accept SMTP messages from hosts that don't have a reverse pointer for their IP, or if their IP is a known dymamic IP. So the originator could forward their mail to a smarthost that is using a fixed IP with a PTR record.

Small businesses given dynamic IPs may have to use their ISP's smarthost even if they are using exchange. Usually a dynamic IP would be troublesome for inbound mail as well, but thanks to dyamic DNS services, there's a workaround.