yarikoptic/fail2ban — comment on commit ed9000c469b4554aab3e9b5365b959520096f3ba
File:  line 0
By d0ru:

Content-Type: text/plain; charset="POSIX"

Obviously I don't know perl.. with ContentType var declaration in sendmail-whois-lines.conf it is correct:
Content-Type: text/plain; charset="en_US.UTF-8"