why are my outgoing ipv4 connections to port 25 blocked?

Posted March 9, 2020 824 views

I installed postfix to send notifications with system information. And i get error in my logs:

 postfix/smtp[3687]: connect to[]:25: Connection timed out

Uptime of my system about 8month

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2 answers

I was and have asked the staff. Not yet received an answer (gmail / hotmail)

  • message from hotmail: centos-s-12vcpu-48gb-sgp1-01 rejected your message to the following email addresses:

    message from gmail: The response from the remote server was:
    550 authentication required

Hello all,

It is possible that port 25 is closed for new accounts. This is something we have been doing to reduce spam on our network. Please do not think that we are accusing you of sending spam, it is more that we simply cannot accurately determine who is going to send it.

Stopping spam is a constant fight, so we have implemented some restrictions on newer accounts. To qualify for the ability to send out email, we do require accounts to wait 60 days before we can look into removing the restriction. Once your account has reached 60 days of stable use, please do reach back out to us so we can look into this for you.

Hope that helps!

  • Good day. I am very sorry that you are inattentively reading messages from your users. I wrote above that my system has been working for more than 8 months. And that was almost a year ago. So how much longer do I need to wait for it to be considered that my account is in stable use ?!
    I am asking you to remove the blocking of their SMTP connections on my account, please.

    • Hey, strelokvc

      Have you already whitelisted the port on the server, perhaps via UFW?

      UFW, or Uncomplicated Firewall, is a simplified firewall management interface that hides the complexity of lower-level packet filtering technologies such as iptables and nftables

      To allow connections on port 25 run:

      sudo ufw allow 25/tcp

      You can check our existing tutorial on how to setup a Firewall with UFW here:

      If you’re still unable to send emails I will recommend you to try using alternative ports as 587 and 465, because a lot of providers will block connections/emails sent without authentication on port 25 as well.

      Hope that this helps!

      by Brian Boucheron
      This tutorial will show you how to set up a firewall with UFW on Ubuntu 20.04.
      • I’m pretty good at servers and networking, if that’s what you mean.
        My ufw is active on the server and has a default policy for outgoing connections - allow.

        # ufw status verbose
        Status: active
        Logging: on (low)
        Default: deny (incoming), allow (outgoing), allow (routed)

        I ran the test again. Outgoing connections to port 25 are still blocked.

        Jan 29 13:13:34 vpn postfix / smtp [10972]: connect to [2607: f8b0: 4024: c02 :: 1b]: 25: Connection timed out