Re: Post.Office mail-blocking measures

John Davies ( (no email) )
Thu, 19 Mar 1998 16:44:41 -0800


>>Does anyone know of a way to have Post.Office 3.1.2 perform a reverse DNS
>>lookup on incoming mail to aid in the prevention of receiving spam? We
>>have SendMail (whatever the latest version is) on one of our Unix machines
>>configured to perform reverse lookup on all incoming mail. If the domain
>>name in the "From:" field cannot be verified, it rejects the mail.
>>Unfortunately, our Post.Office still accepts mail with From addresses like
>>"" and "". We already have huge
>>lists of complete email addresses, domain names, and usernames to block
>>mail from, but there's no way to stop all numeric email addresses from
>>being blocked that I know of...
>I haven't found any way to do it. I have sent numerous emails to
> to have them add reverse DNS lookup on the return addresses
>and they refuse to do it. They keep saying that it takes too much
>processing time. My feeling is that it is worth it. Maybe if enough people
>ask/request/demand/beg for it they will add it.
>Unfortunately, I'm stuck with Post.Office now since I put enough money into
>get my user licenses (though I did get a good deal as an ISP).

MailSite 2.1.5 has this capability:

MailSite does not use a lot of extra CPU or memory to do this. It can add
delays to incoming connections since the connection is not accepted until
the lookup completes. The key is to have a responsive DNS server :-)

Regards, John.