No Such Object available on this agent at this OID

[Drazen M. <dmi...@it...>]

Hi,

I have setup snmpd on one server and everything works fine.
Now I'm trying to implement some custom scripts to report via snmpd and I'm 
using 
exec .1.3.6.1.4.1.2021.53.101.0 mailq /bin/mqueue.sh

but when i call the snmpd server from some other host with 

snmpwalk -v2c -c com_name ip_address .1.3.6.1.4.1.2021.53.101.0

i get this error
UCD-SNMP-MIB::ucdavis.53.101.0 = No Such Object available on this agent at 
this OID

What does that mean?