#Unlock diag user and set password

NETAPP::> security login unlock -username diag

NETAPP::> security login password -username diag

Go into Privileged Mode

NETAPP::> set -privilege advanced

Change to Diag User

NETAPP::> set diag

NETAPP::> systemshell local

Once here you can telnet like normal

NETAPP%>telnet mail.domain.com 25

to Break out 

CTRL C and CTRL D 

Relock Diag Account

NETAPP::> security login unlock -username diag