FIRST-CLASS MAIL LETTER 2017 POSTAGE RATES 2016 POSTAGE RATES INCREASE/DECREASE. First-Class Mail Letter (1 oz.) - Retail/Post Office Rate $0.49 $0.47 $0.02. Metered Mail (1 oz.) - Online Postage Providers and Postage Meters $0.46 $0.465 -$0.005. First-Class Mail Letter - each additional ounce $0.21 $0.21 NO CHANGE.