Manipulate the Sensitivity
field as specified in RFC 2156.
Examples
# Not sensitive.
envelope() %>%
subject("Your daily dose of spam")
# Sensitive personal message.
envelope() %>%
subject("The results from your test") %>%
sensitivity("personal")
# Sensitive private message.
envelope() %>%
subject("Your OTP (don't show this to anybody!") %>%
sensitivity("private")
# Sensitive business message.
envelope() %>%
subject("Top Secret Strategy Document") %>%
sensitivity("company-confidential")