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I'm running an Exchange 2003 server on a Telstra Business internet connection (in Australia).

I'm routing emails through the SMTP connecter, using the host smtp.telstrabusiness.com

When users send single emails to a single recipient, the emails are sent correctly.

However, when users send emails to a distribution list, they bounce back with:

The message could not be delivered because the recipient's destination email system is unknown or invalid. Please check the address and try again, or contact your system administrator to verify connectivity to the email system of the recipient.

One of the people in the list was able to recieve a single email from us just a few minutes afterwards, but did not recieve any of the email that should have come from the distribution list.

Is there a way I can throttle the number of messages that Exchange will send at a time, so as not to appear as spam to Telstra?

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2 Answers 2

It sounds like it's rejecting based on the "to" address ("destination email") rather than rejecting on the basis of volume. When you send via the list, what's the "to" address on the email? Is this one of those list managers that sends "to" the list and BCCs the actual recipients? If so, try replicating that scenario with a single email and see what happens. I'm sure I don't have to tell you that SMTP server administrators have to implement a variety of limitations to minimize spamming, one of which is sometimes to only allow messages to be sent via that SMTP server that are to one of the addresses it serves...

The other thing to check is whether SMTP AUTH is working correctly. Typically if you're correctly authenticating, the other limits are not enforced; but if you don't, they come into play, which can mask the real problem.

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Are these from an internal distribution list or an external distribution list? I'm kind of thinking that your exchange server isn't actually sending any emails at all since you said you are using the smtp connector. IF it's going straight to telstra (instead of hitting your exchange smtp server first) then they won't have any idea what the email addresses are.

I think you might want to us the smtp smarthost instead of the connector.

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