Rejecting mail from localhost.localdomain

[Alex]

Hi,
I was surprised to see I received an email with localhost.localdomain as
the envelope sender. It was a legitimate email, but not from my mail host.

Jun 16 16:15:29 armor policyd-spf[55040]: prepend Received-SPF: None
(mailfrom) identity=mailfrom; client-ip=50.210.225.242;
helo=vw-00301802261d.localdomain;
envelope-from=asterisk@localhost.localdomain; receiver=<UNKNOWN>
Jun 16 16:15:30 armor postfix-110/qmgr[54319]: 6A2E22000341F:
from=<asterisk@localhost.localdomain>, size=1340777, nrcpt=2 (queue active)

Is it safe to add something like this to my helo_checks.pcre:

smtpd_helo_restrictions =
        permit_mynetworks
        check_helo_access ${indexed}helo_checks
        check_helo_access pcre:$config_directory/helo_checks.pcre
        permit
/*.localdomain/               REJECT

and my sender_checks.pcre

smtpd_sender_restrictions =
        permit_mynetworks,
        check_sender_access ${indexed}sender_checks,
        check_sender_access pcre:$config_directory/sender_checks.pcre,
        check_sender_access ${indexed}spamsources,
        check_sender_ns_access ${indexed}blacklist_ns.cf,
        reject_unknown_sender_domain

/*.localdomain/     REJECT

Thanks,
Alex