Voluntary line in message header in callable MAIL interface

[Valentin Likoum]

Hello, is there any way to pass voluntary line to callable MAIL interface to be set in the message header. I need to set "Content-Type: " and "Content-Transfer-Encoding: " lines in the SMTP message header but I see no ways to do it. MAILDEF header file contains undescribed MAIL$_SEND_UFLAGS item. Can it help here?

[Valentin Likoum · Accepted solution]

The solution is multi-line subject field. Thanks Ruslan Laishev for kind help.