Every morning for the last two weeks or more I've had to reboot our Exchange Server and often I have to reboot it again during the day. We use a smarthost for sending our mail out and if I view the queues on Exhange System Manager the Small Business SMTP Connector is in a retry state with "The connection was dropped due to an SMTP protocol event sink". I turned logging up to maximum on ExchangeTransport and the only non-information event in EventViewer is “Message delivery to the host '' failed while delivering to the remote domain 'mail.authsmtp.com' for the following reason: The connection was dropped due to an SMTP protocol event sink. The SMTP verb which caused the error is 'x-exps'. The response from the remote server is ''.”

I stopped using the smarthost during the error condition and all I got was lots of small business connector connections with the same error. I can telnet into mail.authsmtp.com and send a mail during the error state.

Any pointers would be gratefully received.

1 Answer 1


The 'X-EPS' verb is a proprietary Exchange verb, so you are only going to suffer this error when you connect to other servers that offer this verb, mostly other Exchange Servers.

One reason for this error is that you do not have a valid FQDN setup on the SMTP virtual server. To check this go to the properties of your SMTP virtual server, go to the delivery tab and then the advanced button. In here ensure that the 'Fully-qualified domain name' section has a valid domain name in it.

You can also try configuring your SMTP virtual server to send HELO, instead of EHLO. By doing so you will be indicating that your mailserver does not support some extension of the SMTP protocol, including X-EPS, so it will not try to use it. This method will obviously get you round the issue (if X-EPS is at fault), but you won't have all the advanced SMTP extension functions.

  • Hi Sam, Thanks for the response. I had already checked the FQDN in the SMTP properties and no-one has changed that value for months. The "Check DNS" button says its a valid name. Is there another way of checking it's valid?
    – user24944
    Nov 4, 2009 at 12:36

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