$ find ~/Maildir -path '*/cur/*' | wc -l
40745
$ find ~/Maildir -path '*/cur/*' | xargs grep -ih '^content-type:' | grep -io 'charset=[^ >;/]*' > t1
$ wc -l t1
40676 t1
$ cat t1 | tr -d '"' | tr A-Z a-z | sed 's/charset=//' | sort | uniq -c | sort -n
      1 3dus-ascii
      1 3dut=46-8
      1 iso-8859-10
      1 unicode-1-1-utf-7
      1 utf-16le
      1 utf-8
      1 utf8
      1 windows-1250
      2 euc-jp
      2 iso-8859-3
      2 iso-8859-7
      3 euc-kr
      3 iso-8859-5
      4 big5
      4 iso-8859-14
      9 ibm852
     17 ascii
     20 cp-850
     22 iso-2022-jp
     41 gbk
    154 gb2312
    547 windows-1251
    582 iso-8859-2
    631 iso-8859-15
   1189 iso-8859-1
   1349 windows-1252
   7080 us-ascii
  29007 utf-8