On MS Win, inserted bytes was CRLF(0x0D0A) instead of LF.
> Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.5) Gecko/20091129 Shredder/3.0.1pre
Original From: in mail with MDN=on. ({CRLF}==0x0D0A)
> From: =?ISO-2022-JP?B?GyRCT0JFRDh3OTAbKEI=?= <email address hidden>{CRLF}
Tb3 generated following To: in return receipt.
> To: =?ISO-2022-JP?B?GyRCT0JFRDh3OTAbKEI=?={CRLF}
> <email address hidden>{CRLF}
In this case, RFC2822 violation doesn't happen fortunately.
On MS Win, inserted bytes was CRLF(0x0D0A) instead of LF.
> Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.1.5) Gecko/20091129 Shredder/3.0.1pre
Original From: in mail with MDN=on. ({CRLF}==0x0D0A) JP?B?GyRCT0JFRD h3OTAbKEI= ?= <email address hidden>{CRLF} JP?B?GyRCT0JFRD h3OTAbKEI= ?={CRLF}
> From: =?ISO-2022-
Tb3 generated following To: in return receipt.
> To: =?ISO-2022-
> <email address hidden>{CRLF}
In this case, RFC2822 violation doesn't happen fortunately.
Inserted byte(s) looks "new line" used by OS.