Jevons Brown, from St Louis, Missouri, sent packages of cat feces via US mail to employees of companies that failed to hire him.
Brown, a military veteran, was sentenced last week to two years of probation after pleading guilty in August to a misdemeanor charge of mailing injurious articles.
US Postal Inspection Service spokesman Dan Taylor said that investigators tracked 20 similar packages to Brown, 'St Louis Post-Dispatch' reported.
Assistant US Attorney John Bodenhausen said the incident was "not a victimless crime."
Postal workers, people whose mail was next to Brown's packages and employees who received the parcels were all affected, Bodenhausen added.
Both Bodenhausen and Sean Vicente, Brown's public defender, agreed that probation was an appropriate sentence, adding that Brown had recently found a job and had almost no criminal history.