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."
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.