Derek Jennings <[EMAIL PROTECTED]> said: > On Thursday 20 May 2004 01:16, Asa Rossoff wrote: > > Derek Jennings <[EMAIL PROTECTED]> said: > > > Your trouble with upstream SMTP servers rejecting your mail may be > > > because thet are doing a reverse DNS lookup as an anti spam measure. > > > They look at the domain name in your headers, "scoop.local" and do a > > reverse > > > > > DNS lookup to see if it matches the IP address you are attached to. If > > they > > > > > are non consistent your mail is rejected. > > > > > > You can get around the problem by forwarding your mail via tiscali. The > > > tiscali SMTP server knows you are connected to one of its own ISDN lines > > and > > > > > will accept any mail from you. > > > > > > In your /etc/postfix/main.cf add the line > > > > > > relayhost = smtp.tiscali.fr (or whatever it is) > > > > I've heard this rumor before, but I have never had any problems with mail > > delivery direct to various smtp servers as long as I had a fully-qualified > > domain name on my machine. I am not aware of isp's that validate by > > reverse-lookup before accepting a connection, only of many isp's that check > > that your machine id's itself with a fully-qualified internet domain name. > > > > I could be wrong, since I don't handle huge volumes of mail, just personal > > correspondence, but in that, I have had no problems. > > > > Asa > > If you want to enable this feature in your own Postfix server use :- > > smtpd_helo_restrictions = reject_unknown_hostname > > http://www.postfix.org/SMTPD_ACCESS_README.html#lists > > derek
Here's the description of that option, from http://www.postfix.org/postconf.5.html#reject_unknown_hostname : :: reject_unknown_hostname :: Reject the request when the HELO or EHLO hostname has no :: DNS A or MX record. ... It doesn't say that the DNS A or MX record has to match the IP of the connecting machine, just that their is a DNS record (you'll have an MX record for your domain if you intend to receive email) Does it really also compare the ip address from the DNS record to that of the connecting machine? I thought maybe the following restriction offered this feature: dsmtpd_client_restrictions = reject_unknown_client http://www.postfix.org/postconf.5.html#smtpd_client_restrictions :: reject_unknown_client :: Reject the request when the client IP address has no PTR :: (address to name) record in the DNS, or when the PTR record :: does not have a matching A (name to address) record. ... However, on further thought, it appears only to verify that the IP address of the connecting mail client is listed with dns, without regard to the DNS name or the name the client identifies itself with. Asa
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