After updating to Messaging Gateway (SMG) to version 10.7.4, SNMP queries for MIBs associated with the SMG MTA process including message queues return 'No such instance currently exists at this OID'.
$ snmpwalk -v2c -m all -c public smg.local.lab .18.104.22.168.4.1.322.214.171.124.2.1.1
Error 'No Such Instance currently exists at this OID'
This issue is resolved by applying patch 10.7.4-285 as follows:
smg [10.7.4-13]> patch list ... sms-appliance-patch.x86_64 10.7.4-285 symrepo_smg_patches
smg [10.7.4-13]> patch -p 10.7.4-285 install