More and more mail servers are starting to reject email if your outgoing mail server doesn’t have a reverse DNS record or PTR record. You can check if you have one by issuing the following command:
dig -x 127.0.0.1
Obviously, replace the 127.0.0.1 address with the relevant IP address of your mail server. You should receive a response like this:
; <<>> DiG 9.4.1-P1 <<>> -x 18.104.22.168 ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 17269 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;22.214.171.124.in-addr.arpa. IN PTR ;; ANSWER SECTION: 126.96.36.199.in-addr.arpa. 3600 IN PTR myserver.mydomain.com. ;; Query time: 217 msec ;; SERVER: 188.8.131.52#53(184.108.40.206) ;; WHEN: Thu Jul 10 11:09:58 2008 ;; MSG SIZE rcvd: 79
If you don't have one setup, you won't get a response in the ANSWER SECTION - so contact your host and ask them to set one up for you. It can help save a lot of headaches when you get bounce-back messages such as:
Could not deliver the message in the time limit specified. Please retry or contact your administrator.
We use Postfix as a dropin replacement for Sendmail on our servers. We wanted to configure postfix to relay email via our internal mail server for internal email addresses, and send directly if the email address was external.
To do this, follow these steps:
transport_maps = hash:/etc/postfix/transport
[root@triton postfix]# postfix /etc/postfix/transport [root@triton postfix]# service postfix restart
And you should be done!
We have been having problems sending emails from our mail server (running Kerio) to a particular domain over the past few weeks. We kept receiving bounce emails with the following:
550 Rule imposed. Sender using invalid hostname in greeting as per RFC specification.
After trying all manner of solutions, it turned out to be a problem with our Kerio setup. Lots of mail servers are being configured to only accept connections from Fully Qualified Domain Names (FQDN) – we had our mail server setup without a fully qualified address. So we needed to make the following change:
example.com => mail.example.com
To apply this change to our Kerio mail server, we simply changed the setting in Kerio using the following steps:
If you are using a different mail server, consult the associated documentation and ensure you have the mail server setup with a FQDN.