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Unable to deliver message because the maximum hop count was exceeded. This is a potential message routing loop.

Unable_to_deliver_message_because_the_maximum_hop_count_was_exceeded__This_is_a_potential_message_routing_loop__1_2_Rule (Rule)

Knowledge Base article:

Summary

This event indicates that the SMTP component was unable to deliver a message because the message had a hop count greater than that configured on this SMTP virtual server. This is a potential message routing loop.

Sample Event:

Unable to deliver message because the maximum hop count was exceeded.

Causes

Each time a message passes through an SMTP server, the particular SMTP server adds a line to the message header indicating the hop count. This indicates how many SMTP servers that message has already traversed. The SMTP virtual server in Exchange has a default hop count set to 15. This means that if any e-mail message reaches this SMTP server and it has a hop count of 15 in its header, then the message will be rejected.

Resolutions

The hop count for an SMTP virtual server in Exchange can be configured to be between 10 and 256. If your topology is complex, and the messages in your organization must be routed through several servers before being sent out to the Internet, you can suitably increase the hop count of the SMTP virtual server.

External

For more information about MSExchangeTransport event 717, see:

Element properties:

TargetMicrosoft.Exchange.Protocol.SMTP
CategoryEventCollection
EnabledTrue
Event_ID717
Event SourceMSExchangeTransport
Alert GenerateTrue
Alert SeverityWarning
Alert PriorityNormal
RemotableTrue
Alert Message
Unable to deliver message because the maximum hop count was exceeded. This is a potential message routing loop.
{0}
Event LogApplication

Member Modules:

ID Module Type TypeId RunAs 
EventDS DataSource Microsoft.Windows.EventProvider Default
GenerateAlert WriteAction System.Health.GenerateAlert Default

Source Code:

<Rule ID="Unable_to_deliver_message_because_the_maximum_hop_count_was_exceeded__This_is_a_potential_message_routing_loop__1_2_Rule" Enabled="onEssentialMonitoring" Target="Exch2003Core!Microsoft.Exchange.Protocol.SMTP" ConfirmDelivery="false" Remotable="true" Priority="Normal" DiscardLevel="100">

  <Category>EventCollection</Category>

  <DataSources>

    <DataSource ID="EventDS" TypeID="Windows!Microsoft.Windows.EventProvider">

      <ComputerName>.</ComputerName>

      <LogName>Application</LogName>

      <Expression>

        <And>

          <Expression>

            <SimpleExpression>

              <ValueExpression>

                <XPathQuery>Channel</XPathQuery>

              </ValueExpression>

              <Operator>Equal</Operator>

              <ValueExpression>

                <Value>Application</Value>

              </ValueExpression>

            </SimpleExpression>

          </Expression>

          <Expression>

            <SimpleExpression>

              <ValueExpression>

                <XPathQuery>PublisherName</XPathQuery>

              </ValueExpression>

              <Operator>Equal</Operator>

              <ValueExpression>

                <Value>MSExchangeTransport</Value>

              </ValueExpression>

            </SimpleExpression>

          </Expression>

          <Expression>

            <SimpleExpression>

              <ValueExpression>

                <XPathQuery>EventDisplayNumber</XPathQuery>

              </ValueExpression>

              <Operator>Equal</Operator>

              <ValueExpression>

                <Value>717</Value>

              </ValueExpression>

            </SimpleExpression>

          </Expression>

        </And>

      </Expression>

    </DataSource>

  </DataSources>

  <WriteActions>

    <WriteAction ID="GenerateAlert" TypeID="SystemHealth!System.Health.GenerateAlert">

      <Priority>1</Priority>

      <Severity>1</Severity>

      <AlertOwner>$Data/PublisherName$</AlertOwner>

      <AlertMessageId>$MPElement[Name="Unable_to_deliver_message_because_the_maximum_hop_count_was_exceeded__This_is_a_potential_message_routing_loop__1_2_Rule.AlertMessage"]$</AlertMessageId>

      <AlertParameters>

        <AlertParameter1>$Data/EventDescription$</AlertParameter1>

      </AlertParameters>

      <Suppression>

        <SuppressionValue/>

      </Suppression>

    </WriteAction>

  </WriteActions>

</Rule>