I run this command
Set-OwaMailboxPolicy -Identity OWAMailboxPolicy-Default -AllowedFileTypes .prg
the I run this command
get-OwaMailboxPolicy | select blockedfiletypes |Export-Csv D:\name.csv
and notice that .prg is still in the block list. In addition we still receive a message like this
FILE DELETED
part.prg has been removed since it was found to match the FILE FILTER= ExchangeLabs File Filter List 1: <in> *.prg file filter.