SendMail in BusyBox v1.19.3

[Rick]

I'm having some difficulty in interpreting the latest usage syntax for
SendMail. I'm only familiar with the version in the BusyBox of a couple
years ago, which included more switches. The old syntax for my purposes was:

sendmail -S"smtp server address" -f"from email address" -F"From name"
-d"sender's domain" -s"Subject" -m"content of the message"
sendmailhere at domain.com

Of the above switches, apparently only -S and -f survive in the current
version, depending on what -o "Various options" means. So, I'm a little
puzzled about how to go about things now, particularly if there's no -m (I
think redirection of a file containing the message might be involved now,
but I failed at that as well).

Could someone list a concrete example for me?  Thanks.