>Our Imail server can't send email to a few large corporates' recipients. At >last, with the help of Scott, I find the root of the problem, our mail >server's IP don't have a PTR record. That means that you can't use our mail >server's IP to do a reverse DNS search.
I should clarify this last sentence -- it means that the IP address of your server does not have a reverse DNS entry (nobody will connect to your IP during a reverse DNS lookup, unless that IP happens to be a DNS server used in the lookup). >Now, our new problem is that we can't create a PTR record for our mail >server's >IP. I have try my best to do it. But failed. *Only* your ISP (or bandwidth provider) can get the reverse DNS entry set up. Either they can set up the reverse DNS entry on their DNS servers, or they can delegate authority for your IP(s) to your DNS servers. >Our ISP create a PTR record on their DNS server. It does work, but ONLY on >their DNS server. That means that your ISP has no clue what they are doing, and you should look for another ISP. Specifically, if it only works on their DNS server, they are not authoritative for your IPs -- but as your ISP, they can't get the IPs assigned to you without being authoritative for them! >I also try to apply for a new domain name, then create a PTR record for >it. I buy >one at www.domainbank.com at the cost of $35.-. Then we pay $10 for creating >DNS record on their DNS servers. But, at last they told us they can create >MX and A record for us, and they can't create a PTR record for us. That is correct. With reverse DNS lookups, the registrar is not involved. All IPs are distributed among 3 organizations -- ARIN, APNIC, and RIPE (each covering roughly 1/3 of the world). These three organizations hand out the IPs to ISPs and other organizations, who then hand them out to you. So for a reverse DNS lookup, the DNS resolver will ask ARIN "Who does this IP belong to?" and ARIN will say (for example) "This IP belongs to APNIC -- contact them at one of these addresses". The DNS resolver will then connect to one of those addresses at APNIC, and ask "Who does this IP belong to?". APNIC will say "It belongs to Acme ISP -- contact them at one of these addresses". The DNS resolver then asks Acme ISP "Who does this IP belong to", and Acme ISP says "Oh, I know that IP! It is mail.example.com". So from the way that the reverse DNS lookups work, a domain registrar has no control -- only the ISP does. If you go to http://www.DNSstuff.com and use the Reverse DNS Lookup, it will show you exactly how the lookup is done. It should show you who to contact (your ISP) to get the reverse DNS entry. -Scott --- Declude: Anti-virus, Anti-spam and Anti-hijacking solutions for IMail. http://www.declude.com --- [This E-mail was scanned for viruses by Declude Virus (http://www.declude.com)] Please visit http://www.ipswitch.com/support/mailing-lists.html to be removed from this list. An Archive of this list is available at: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Please visit the Knowledge Base for answers to frequently asked questions: http://www.ipswitch.com/support/IMail/
