Messages can be routed through many different servers before reaching their final destination. The number of servers a message passes through is called the hopcount. As an administrator, you can control the maximum allowable hop count and you'll usually want to do this to prevent a message from being repeatedly misrouted.
The default maximum hop count is 15, which works well for most network configurations. However, if users frequently get nondelivery reports that state that the maximum hop count was reached and the message wasn't delivered, you may want to consider increasing the maximum allowable hop count. The number of Received lines in the message header determines the total hops.

Caution: Don't automatically increase the hop count without first examining the network. Nondelivery reports due to the hop count can also point to network problems. You can run a traceroute command (tracert hostname) to the destination mail server to help determine if a misconfigured or down network is to blame for the delivery problem.

You can view or set the maximum hop count by completing the following steps:

1. Start System Manager. If administrative groups are enabled, expand the administrative group in which the server you want to use is located.
2. In the console tree, navigate to the Protocols container. Expand Servers, expand the server you want to work with, and then expand Protocols.
3. In the console tree, expand SMTP. Right-click the virtual server that you want to work with, and then select Properties. The default SMTP virtual server controls message delivery for the default domain.
4. In the Delivery tab, click Advanced. This displays the Advanced Delivery dialog box.
   
5. If you want to change the hop count, type a new value in the Maximum Hop Count field. Valid values are between 10 and 256.
6. Click OK twice.