Quoting
http://exim.org/exim-html-current/doc/html/spec_html/ch-the_exim_command_line.html
-i
This option, which has the same effect as -oi, specifies that a
dot on a line by itself should not terminate an incoming, non-SMTP
message. I can find no documentation for this option in Solaris 2.4
Sendmail, but the mailx command in Solaris 2.4 uses it. See also -ti.
According to SUNOS5.4, Maintainence Commands, Sendmail(1M),
modified 16 Feb 1994, Page 1M-529
at
https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf
i Do not take dots on a line by themselves as a message terminator.
It is related to Solaris 2.4 by
https://docs.oracle.com/cd/E19457-01/
--
u34