Local mail server not sending emails

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Ever since the ISP was changed, I am having issues with our local mail server (Fedora/sendmail). The log states connection timed out with domain.com when I try to send test mail to abc@domain.com. But I can successfully ping domain.com from the Fedora box. It's hosted by a third party web hosting site. When I send the test message, I get the Message accepted for delivery response from the mail server but it never gets delivered. I think some setting is missing somewhere and I am a Linux newbie. Please advice.

Port 25 is open and listening. The smtp server receives incoming mails though. But can't send out emails.

yonikawa

Posted 2016-08-29T15:06:36.530

Reputation: 119

Answers

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Can you telnet smtp port on host.domain.com host? Do you get SMTP greeting message?

telnet host.domain.com 25

NO => Your outgoing smtp connections may be blocked (by your ISP) to stop outgoing spam.

AnFi

Posted 2016-08-29T15:06:36.530

Reputation: 771

Yeah, that's probably it. Configure the system to use a different port for secure send (587, or for SMTP-SSL use 465). 25 is blocked by pretty much EVERY ISP as an unsecured relay mostly used for spam these days. – dr.nixon – 2016-08-29T18:05:16.773

@Andrzej A. Filip : Thanks for the response. Seems like that's the problem. I tried changing the sendmail port to 587 using the sendmail.mc file and restarted the service. How do I add the port to iptables to bypass the firewall? I am using Fedora 3 version installed over 10 years ago. – yonikawa – 2016-08-30T15:24:28.323

@dr.nixon : So I ended up calling ISP and they unblocked the port 25. Now I can send test messages successfully using Outlook to the mail server and subsequently receive it on my email address. But when I try to test the mail server directly from the machine, for some reason the relay is root@localhost compared to relay =abc.com using Outlook. abc.comis our external smtp server, its defined in etc/hosts, sendmail.mc etc. but still its not resolving it properly. Any tips? – yonikawa – 2016-08-30T22:47:48.567

What is reported by commands hostname and hostname --fqdn? – AnFi – 2016-08-31T19:41:06.577

@AndrzejA.Filip : I fixed it. Some how my loopback adapter was turned off and hence it wasn't resolving the names properly. Once I turned it back ON, now it works. – yonikawa – 2016-08-31T19:43:20.583

Asked: 2016-08-29T15:06:36.530

Viewed: 104 times

Active: 2016-08-29T16:05:18.907