Centos 7 - Sendmail not working

Question

I'm trying to setup sendmail on my centos 7 server, but it's failing for some reason. I've opened port 25/tcp on firewall-cmd and selinux is disabled as well. It's still not working... /var/log/maillog logs:

Jul 25 14:14:34 mail sendmail[12274]: u6PBEYlI012274: [email protected], size=101, class=0, nrcpts=1, msgid=<[email protected]>, relay=root@localhost
Jul 25 14:14:34 mail sendmail[12275]: NOQUEUE: tcpwrappers (localhost, 127.0.0.1) rejection
Jul 25 14:14:34 mail sendmail[12274]: u6PBEYlI012274: [email protected], [email protected] (0/0), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=30101, relay=[127.0.0.1] [127.0.0.1], dsn=5.0.0, stat=Service unavailable
Jul 25 14:14:34 mail sendmail[12274]: u6PBEYlI012274: u6PBEYlJ012274: DSN: Service unavailable
Jul 25 14:14:34 mail sendmail[12274]: u6PBEYlJ012274: [email protected], delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=31125, relay=[127.0.0.1], dsn=5.0.0, stat=Service unavailable
Jul 25 14:14:34 mail sendmail[12274]: u6PBEYlJ012274: u6PBEYlK012274: return to sender: Service unavailable
Jul 25 14:14:34 mail sendmail[12274]: u6PBEYlK012274: to=postmaster, delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=32149, relay=[127.0.0.1], dsn=5.0.0, stat=Service unavailable
Jul 25 14:14:34 mail sendmail[12274]: u6PBEYlJ012274: Losing ./qfu6PBEYlJ012274: savemail panic
Jul 25 14:14:34 mail sendmail[12274]: u6PBEYlJ012274: SYSERR(root): savemail: cannot save rejected email anywhere

Thanks to @Andrzej A. Filip's answer i'm now getting this in the logs:

Jul 25 17:26:00 mail sendmail[3812]: u6PEPxur003812: [email protected], size=102, class=0, nrcpts=1, msgid=<[email protected]>, relay=root@localhost
Jul 25 17:26:00 mail sendmail[3813]: u6PEQ0Bs003813: from=<[email protected]>, size=347, class=0, nrcpts=1, msgid=<[email protected]>, proto=ESMTP, daemon=MTA, relay=localhost [127.0.0.1]
Jul 25 17:26:00 mail sendmail[3812]: u6PEPxur003812: [email protected], [email protected] (0/0), delay=00:00:01, xdelay=00:00:00, mailer=relay, pri=30102, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (u6PEQ0Bs003813 Message accepted for delivery)

But the mails are still not coming to destination...

Solution

Your sendmail seems to use tcpwrappers. tcpwrappers seem to reject email connection to 127.0.0.1:25.
Such connections are used to pass email submitted via sendmail command to local sendmail daemon.

FIX:
Inspect and fix tcpwrappers configuration files: /etc/hosts.allow and /etc/hosts.deny.

Comments

[Jojo01]

I put sendmail:ALL into hosts.allow, and now it says sent in the maillog, but i'm still not getting it into my mailbox.

[AnFi]

It seems that the message stays in sendmail's queue - there is no trace of delivery attempts by main sendmail daemon. You can as root push messages in the queue in verbose mode. Use /usr/sbin/sendmail -v -q

[Jojo01]

I'm getting pastebin.com/C06n4W6u when i run that command. Are there other ports than 25 to open?

[AnFi]

It looks like your outgoing smtp connections are blocked (firewalled out). Try to telnet port 25 at the host to check if it is sendmail problem. Can you telnet port 587 at smtp.gmail com?