CVE-2023-51764: Improvements for inbound SMTP smuggling defense.
Reject or restrict input lines from an SMTP client that end in bare new line.
Replace each stray <CR> or <LF> character in message
content with a space character, to prevent outbound SMTP smuggling
To prevent the SMTP smuggling vulnerability, the option "smtpdforbidbare_newline = reject" must be set.