Checking Sender's PTR / rDNS record - antispam

[alfista]

Hi All,

Can anyone point me to a tutorial for rejecting incoming email if the sender's PTR record does not point to the sender's reported hostname? I just had to correct mine and it seems like a good way of helping fight spam.

Regards,

Jason

[JasonWarren]

Hi,
I would also like to know...is there a 'How to' anywhere?
Thanks

[jaime.pinto]

dnl # We strongly recommend not accepting unresolvable domains if you want to
dnl # protect yourself from spam. However, the laptop and users on computers
dnl # that do not have 24x7 DNS do need this.
dnl #
FEATURE(`accept_unresolvable_domains')dn

Look for the above feature line in the /etc/mail/sendmail.mc file and put a comment in front of it. And re-generate sendmail.cf and reload sendmail services.