qmail-injectに流すデータはCRLFじゃなくてLFじゃないとダメ

今まで知らなかった…

qmail-smtpd converts the SMTP newline convention into the UNIX newline convention by converting CR LF into LF. It returns a temporary error and drops the connection on bare LFs; see http://pobox.com/~djb/docs/smtplf.html.

End-of-file in SMTP is encoded as dot CR LF. A dot at the beginning of a line is encoded as dot dot. It is impossible in SMTP to send a message that does not end with a newline. qmail-remote converts the UNIX newline convention into the SMTP newline convention by inserting CR before each LF.

で、

 qmail-smtpd --- qmail-queue --- qmail-send --- qmail-rspawn --- qmail-remote
               /                     |      \
qmail-inject _/                 qmail-clean  \_ qmail-lspawn --- qmail-local

なので、qmail-injectに流すデータの行末をCRLFにすると意図しない行末コードのメールが届くというわけです。