my server sent an e-mail to my gmail address, but apparently Gmail denied to deliver the message:

Subject: Undelivered Mail Returned to Sender
Reporting-MTA: dns; my.hostname.here
X-Postfix-Queue-ID: E0BFD340054B
X-Postfix-Sender: rfc822; [email protected]

<[email protected]>: host gmail-smtp-in.l.google.com[] said:
550-5.7.1 This message does not have authentication information or fails to
pass 550-5.7.1 authentication checks
. To best protect our users from spam,
the 550-5.7.1 message has been blocked. Please visit 550-5.7.1
https://support.google.com/mail/answer/81126#authentication for more 550
5.7.1 information. c14si*****qtd.55 - gsmtp (in reply to end of DATA

Please how to make Linux send the e-mail so Gmail accept it?


So far this is what i did:

1. in my server provider control panel i setup rDNS(PTR) record for my server IP so it resolve to my server hostname: (my.hostname.here)
2. on the server where i host hostname.here website i went into DNS zone file (DNS section) and created new DNS record type "A", name "my" (part of my hostname) and value "" (my server IP)

---- So that way IP resolve to hostname (thanks to rDNS(PTR) record) and also hostname resolve to IP thanks to DNS A record i created.

Now i set hostname on my linux server: $ hostname my.hostname.here

Now i make sure my public server IP is set on my FQDN, hostname:

$ cat /etc/hosts localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 my.hostname.here my

Restart networking, maybe not needed:

$ service network reload (or: $ service networking reload)

Check hostname of my server (may be needed to exit terminal and enter it again for changes to reflect):

$ hostname

Verify DNS A record i created earlier that it resolve to my server IP:

$ host my.hostname.here

Verify rDNS(PTR) i created in my server provider web control panel:

$ host domain name my.hostname.here.

---- SUMARY: i set hostname, hostname resolve to my IP, IP resolve to hostname thanks to rDNS record, hostname resolve to IP thanks to DNS A record. I waited some days and see e-mail is delivered, no problem.