> On 12-21-2021 9:38 am, White, Daniel E. (GSFC-770.0)[NICS] wrote:
> How do I stop junk like…
> HELO example.com
> … without having to create a huge "check_helo_access" table ?
In my opinion it would be better to focus on the client PTR than to worry about
HELO. I have seen a small percentage of invalid HELO from valid email sources.
Even outlook.com once in awhile has an invalid HELO I assume from employee
error. But to tighten up on HELO look at...
smtpd_helo_required = yes
unknown_hostname_reject_code = 550
smtpd_helo_restrictions =
reject_non_fqdn_helo_hostname
reject_unknown_helo_hostname
http://www.postfix.org/postconf.5.html#smtpd_helo_required
http://www.postfix.org/postconf.5.html#unknown_hostname_reject_code
http://www.postfix.org/postconf.5.html#reject_non_fqdn_helo_hostname
http://www.postfix.org/postconf.5.html#reject_unknown_helo_hostname
Another simple spam blocking option is using a public blacklist RBL, which
might not be free if you have large volumes of email.
smtpd_recipient_restrictions =
reject_rbl_client zen.spamhaus.org=127.0.[0..2].[0..255]
reject_rhsbl_client dbl.spamhaus.org=127.0.[0..2].[0..255]
reject_rhsbl_helo dbl.spamhaus.org=127.0.[0..2].[0..255]
http://www.postfix.org/postconf.5.html#reject_rbl_client
http://www.postfix.org/postconf.5.html#reject_rhsbl_client
http://www.postfix.org/postconf.5.html#reject_rhsbl_helo
https://www.spamhaus.org/zen/
https://www.spamhaus.org/dbl/
Spamhaus is just one company you can use, there are several others, I am not
making any claims or recommendations to them over any other. They do allow free
usage for low volume servers which is why i use them.
