mail relay question

davesnb used Ask the Experts™
Hello EE,

I have IIS configured for smtp relay, i have "" configured for "forward all mail to smart host" . So my question is , when the email is sent to the forwarder , does the forwarder receive the message and open a new transaction from the ? What are the steps for how the transaction occurs to the recipient email server?

For example, if the recipients mail logs show fails to end with "." on a line by itself, is this my IIS virtual smtp server or the forwarder?
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Software and Hardware Engineer
yes. IIS "spools" the mail locally, folds in anything added by drop into the delivery directory, and sends it outbound using a worker thread. any errors in the logs of an upstream are down entirely to your IIS SMTP engine (which isn't the best, really) or intermediate hosts. That said, some firewalls (and most cisco devices) are notorious for causing issues like this - look for lines like "inspect esmtp" and "smtp fixup" and try disabling them to see if the issue goes away.  other devices (such as fortinet) are known to have similar issues if you aren't using a vanilla build of exchange....

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