Sebastian Ries a écrit : > Hi there > > I just want to know some opinions on the following DNS Setup for a mail > server: > > # host -t MX example.com > example.com mail is handled by 100 mail.example.com. > > # host mail.example.com > mail.example.com is an alias for hostname.example.com.
wrong. an MX must not be a CNAME. your mail may be blocked because of this. More generally, there is not much benefit from using a CNAME inside a single zone (both alias and cname are in the same zone) because you can use a script to convert the CNAME record to a "real" record. CNAME is mostly useful when the alias points to a record in a remote zone (that is not under your control). > hostname.example.com has address 1.2.3.4 > > # host 1.2.3.4 > 4.3.2.1.in-addr.arpa domain name pointer hostname.example.com. > > The mailserver (postfix) connects saying it is hostname.example.com. > > > Should this be a correct setup? > for sending mail? yes. > One partner we want to send mails to does BOUNCE mails with > 554 5.7.1 DNS Blacklisted by in-addr.arpa (in reply to MAIL FROM > command) the error message is useless. Who is in-addr.arpa and why is he blocking mail? :) > Do you think this is correct? > > I think this also prevents from getting mail from googlemail: if the reason is that the MX name differs from the "hostname", then he wouldn't get mail from any large site (including all ISPs). The MX is for receiving mail, not for sending mail. Sites who have the resources use different systems for these two _different_ functions (first, you don't want to block outbound mail if your MX is overloaded or DOSed. second, the outbound mail server can be firewalled so that it is only accessible from specific networks, ... etc). > [EMAIL PROTECTED]:~$ host -t MX googlemail.com > googlemail.com mail is handled by 5 gmail-smtp-in.l.google.com. > googlemail.com mail is handled by 10 alt1.gmail-smtp-in.l.google.com. > googlemail.com mail is handled by 10 alt2.gmail-smtp-in.l.google.com. > googlemail.com mail is handled by 50 gsmtp147.google.com. > googlemail.com mail is handled by 50 gsmtp183.google.com. > [EMAIL PROTECTED]:~$ host gmail-smtp-in.l.google.com. > gmail-smtp-in.l.google.com has address 209.85.129.27 > gmail-smtp-in.l.google.com has address 209.85.129.114 > [EMAIL PROTECTED]:~$ host 209.85.129.27 > 27.129.85.209.in-addr.arpa domain name pointer fk-in-f27.google.com. > > Is this true? > > Regards > Sebastian Ries >
