SMTP Session Delays
The SMTP session delay exceeds the critical value set in Expert Thresholds. The "session delay" metric combines network latency (i.e., the time spent waiting for data to traverse the network) and application processing time (i.e., the time spent waiting for the server or application to respond to a request). Application Response Time for SMTP is tracked with a separate Expert Threshold.
Possible reasons for the event:
If the Expert Threshold for application processing time is also being exceeded, the slowdown is probably the result of a server or application configuration issue. Perhaps the server hardware is overloaded with messages. The SMTP or sendmail logs may be able to shed light on how the server is behaving during message transactions.
If application processing time is within reasonable limits, network latency accounts for the bulk of the delay, and you should look for problems with the network. Do you have enough bandwidth between the mail server and all the clients that use it? Are the routers between the systems configured correctly?