[gentoo-user] arpwatch changed syntax?

[Caveman Al Toraboran <toraboracaveman@protonmail.com>]

hi.


background:
-----------

previously, i used to run it by this:

    > arpwatch -i enp7s0 -m caveman@domain.com -s /usr/sbin/sendmail

but now, after some update, apparently this
doesn't work any more.

what seems to have changed is:

    * "-m" is replaced by "-w" or "-W".
    * "-s" doesn't specify sendmail path, but is
      rather only a flag to suppress "reports sent
      by email".

if i update the command into:

    > arpwatch -i enp7s0 -w caveman@domain.com

then, it runs normally, but, it fails to send
emails, with this error:

    > execl: sendmail: No such file or directory

`whereis sendmail`:

    > sendmail: /usr/sbin/sendmail /usr/lib/sendmail /usr/lib64/sendmail /usr/share/man/man1/sendmail.1.bz2


questions:
----------

Q1: what happened that caused this syntax change?
    e.g. is it an update from upstream?  or is it
    a totally new app written by other devs?  or
    am i hallucinating (pretty sure it used to
    work tho)?

Q2: is there any better tool to monitor arps and
    to email me when interesting things happen?

thanks a lot for your time.

rgrds,
cm.