When a message is delivered, it may be routed to a number of
servers before reaching its final destination. The number of
servers a message passes through is called the hop count, which you
can designate.
After the hop count is set, the SMTP virtual server counts the
number of Received lines in the message header. When the number of
Received lines exceeds the maximum hop count setting, the message
is returned to the sender with an NDR.
Right-click the SMTP virtual server, and then click
Properties.
On the Delivery tab, click Advanced.
In Advanced Delivery, in Maximum hop count, type
a value for the number of hops a message can take between the
source and destination servers. The default is 15 hops.