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No, I don't think I've all those information configured. I've just a static IP that the company has and we're planning to host a dozen of domains into it (none yet active) and I thought to go ahead with virtual domains setup.
So, what should I do is I need to have a DNS record that points to the IP of the machine, am I correct?
reject_unknown_sender_domain Reject the request when the sender mail address has no DNS A or MX record. The unknown_address_reject_code parameter specifies the response code for rejected requests (default: 450). The response is always 450 in case of a temporary DNS error.
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. The unknown_client_reject_code parameter specifies the response code to rejected requests (default: 450).
address to name = rDNS
Maybe you don't lock down your mail server against SPAM, but some of us do...
The mail server replying to the message causes backscatter so you may not receive a failed message from Gmail, hotmail, Yahoo mail, etc. if you haven't bothered to configure the basics such as DNS.
If the ISP his company is using for their corporate Internet connection is blocking ports.. it's time for a new ISP..
I'll stand by my statement that all three DNS records are required.
I know what postfix restrictions are (see my postfix-logwatch utility).
And using them, you should know that rejects from those smtpd_sender_restrictions generate more verbose reject responses, which postfix will log as a more informative message, with SMTP reply codes, and even DNS codes.
A connection to the IP address given by the IP works just fine.
$ telnet 18.104.22.168 25
Connected to wa-in-f114.google.com.
Escape character is '^]'.
220 mx.google.com ESMTP m25si6437596waf.41
250-mx.google.com at your service, [22.214.171.124]
If the OP tries this same test, he will find Connection refused. Connection refused comes from the networking library software of the OS; a socket connection cannot be established. This does not come from Postfix. Furthermore, the remote MTA never had a chance to reject, because the socket connection was never made.
I did that from my mailserver, from outside I can not connect to that server
telnet mail.domain.tld 25
Connected to mail.domain.tld (xxx.xxx.xxx.xxx).
Escape character is '^]'.
220 mail.domain.tld ESMTP Postfix
mail from: firstname.lastname@example.org
rcpt to: email@example.com
354 End data with <CR><LF>.<CR><LF>
250 Ok: queued as 2349C61E21
I'm sorry, I'm confused as to what you've accomplished. Your domain names above are obfuscated, so I'm not sure what the above proves, other than you get a connection refused from the host at apparently 126.96.36.199. I'm further confused by "from outside I can not connect to that server". Outside where? I thought we were trying to establish if from your postfix server machine can telnet to the IP 188.8.131.52, as in: