Hello.
In Japan, most Japanese e-mail is written in ISO-2022-JP.
But mail shield of avast! 5 writes note in Shift_JIS.
Therefore, note is displayed by mistake.
Please refer RFC1468
http://www.ietf.org/rfc/rfc1468.txt
#Sometimes utf-8, utf-7, shift_jis and euc-jp are used.
Best Regards.