Dr. Panda Mailman (iOS or Android) - FREE
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https://itunes.apple.com/us/app/dr-panda-mailman/id918035581
https://play.google.com/store/apps/details?id=com.tribeplay.pandapostman
https://itunes.apple.com/us/app/dr-panda-mailman/id918035581
https://play.google.com/store/apps/details?id=com.tribeplay.pandapostman