Alternative Job Titles: Lockbox Machine Operator, Mail Processing Operator, OPEX Operator, Lockbox Operations Associate, Mailroom Operator, Document Processing Operator, Scanning Operator, Payment Processing Associate, Mail Extraction Operator, Production Machine Operator, Treasury Operations Associate, Lockbox Clerk, Operations Processor, Mail Sort Operator, Financial Processing Associate. Throughout the past 35+ years, MMC, one of the most trusted names in workforce management services, has successfully delivered strategic solutions to large and small businesses in numerous industries.