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BlogLinodeUna nueva política para ayudar a combatir el spam

Una nueva política para ayudar a combatir el spam

En Linode, estamos muy orgullosos de nuestros equipos de Atención al Cliente y Confianza y Seguridad y del trabajo que realizan juntos. Son equipos formados por personas reales que comparten un objetivo importante: mantener nuestra plataforma segura y libre de abusos y fraudes, y elaborar políticas que mantengan la seguridad de nuestros clientes. Esto significa que cuando envías un correo electrónico a, puedes esperar que una persona real te atienda, normalmente en cuestión de minutos, un miembro de todo un equipo que ha recibido una amplia formación para entender todas las complejidades que puede conllevar la gestión de los abusos, y que puede responder a las denuncias con empatía y urgencia.

Uno de los problemas más comunes para nuestros equipos (y nuestra industria) es el abuso del correo electrónico spam. Constituye una parte importante de los problemas que nuestro equipo de Confianza y Seguridad tiene que gestionar, y es un problema que cada año es más difícil de resolver, ya que los usuarios fraudulentos se adaptan a los nuevos métodos para detener y bloquear el abuso. A medida que Linode ha ido creciendo, hemos reflexionado sobre lo que podemos hacer para disuadir a los spammers y a los usuarios fraudulentos de utilizar nuestra plataforma.

En respuesta a este problema, a partir de hoy, los Linodes de las cuentas de clientes recién creadas tendrán restringidas por defecto las conexiones salientes de los puertos 25, 465 y 587. Este cambio solo afecta a los clientes que se registren a partir de hoy; si ya es cliente de Linode , no se realizará ningún cambio en los Linodes existentes o nuevos.

Restringir el acceso a estos puertos, que se utilizan para el envío de correo a través de SMTP, contribuirá en gran medida a reducir la cantidad de spam transmitido desde nuestra plataforma. Sin embargo, también reconocemos que muchos clientes tienen una necesidad legítima de enviar correo, y queremos ayudarles a hacerlo. Para esos clientes, el proceso para eliminar estas restricciones es sencillo: 

  1. Configure registros A y DNS inversos válidos para los Linodes que desea utilizar para el envío de correos.
  2. Abre un ticket de soporte y facilítanos algunos datos básicos (la información que te pediremos está descrita en nuestra guía "Cómo gestionar un servidor de correo").

Nuestro equipo de soporte revisará su solicitud y, si todo parece correcto, eliminará las restricciones del puerto SMTP para que pueda ponerse en marcha.

Al desplegar esta nueva política, nuestro objetivo es equilibrar la necesidad de mantener la seguridad de nuestra plataforma con la comprensión de que muchos de nuestros clientes tienen necesidades legítimas de enviar correo. Queremos que Linode sea la mejor plataforma en la nube para los desarrolladores y los clientes para los que construyen. Al mantener a los malos actores fuera y nuestro espacio IP libre de spam y abuso, esperamos ofrecer una experiencia en la nube más limpia, más eficiente y, en última instancia, mejor para usted.

Comentarios (27)

  1. Author Photo

    There’s a confusing discrepancy between this article and the “Running a Mail Server” guide. Here is saying connections to (INCOMING) those ports will be blocked. The guide says OUTBOUND connections will be blocked.

    Which is it?

    The former makes more sense as it helps stop accidental mail servers on the network. The later doesn’t as it prevent sites/servers from sending emails to administrators. (Like logcheck, update notices for websites, etc.)

    • Jim Ackley

      Hey Paul. I’ve just updated the post – we block outbound connections on those ports, not inbound connections.

      • Author Photo

        Hi, I don’t understand how this works. I am running OpenVPN on my Linode and when I use it, I can’t email out from thunderbird. Can you explain how I can allow the connections? Because none of this makes sense unless I was using a domain/email

  2. Author Photo

    Next step, let ML algorithm decide who to unblock? Anyway, very stupid decision. Customers pay you money. You’re a commodity interchangeable service. If you make stupid additional barriers for customers, they will just live to your rivals. Nobody wants to wait and talk to your support, justify himself and be dependent on someone’s will.

    • Author Photo

      Thank you for sharing your thoughts with us. This policy was created out of a need to address abuse on our platform in a comprehensive way, and we carefully weighed this against industry practices. We are, and always will be, a team of real humans, and we will respond to every request.

      If you would like to reach out to us immediately to address these concerns on your account, we are available 24/7 via phone.

      • Author Photo

        Can I suggest that moving your main site to Cloudflare may not look the best to some from an anti-spam (and anti-abuse in general) perspective, and perhaps could also suggest to others a possible lack of confidence in your infrastructure’s ability to handle your site’s traffic by itself?

        Or could it be in part because your new site has a significantly large bandwidth usage and they help you with the static content bandwidth?

  3. Author Photo

    Spammers send mail, that is, make outgoing connections to other mail servers, so I’m not sure how blocking incoming connections helps.

    • Jim Ackley

      Hey Kenyon. Just updated the post to clarify – we block connections *from* Linodes (e.g. outbound connections), not inbound. Sorry for the confusion!

      • Author Photo

        Ah, but mail servers don’t usually make outgoing connections to ports 465/587…mail client apps do.

        I think I understand the change, having seen quite a few SMTP bruteforce attempts in my own mailserver’s logs, but it still doesn’t entirely *fit* the explanation provided.

        I think that for many users an intermediate unlock level where 465/587 are allowed but 25 is still blocked would make sense, e.g. if they’re not running a mail server at all but just want to use msmtp for relaying Cron mail through Gmail, or using Amazon SES, or such.

        • pwoods

          That’s an interesting idea and something we can consider as we review the implications of this change. I appreciate you taking the time to share your thoughts on how to better serve legitimate users. I’ve shared your thoughts with the rest of the company to review.

  4. Author Photo

    Port 587 should not be blocked, this port is not used for receiving unauthenticated mail and was created specifically to allow authenticated mail from senders so that networks can block port 25 for non-mail-server traffic.

    To be clear, port 587 cannot be used to send spam.

    • pwoods

      While most mail servers ask for authentication, port 587 can be used as a way to send spam. Port 587 is often used for outgoing unencrypted mail from an SMTP server, and is why we’ve chosen to include it in these ports that are initially blocked.

  5. Author Photo

    Good move (both actions), if it helps Linode users running legitimate mail servers getting their non-spam mail accepted on the internet. This has been a problem in the past; also due to other actors (e.g. Google) being entirely non-transparent about how they decide to drop your mail.

  6. Author Photo

    When you say we need a valid A record, does that mean we have to use your DNS service in order for the ports to be unblocked? What if we use DNS servers provided by our registrar, a third party, or even a server we operate? Will there be any accommodations for those customers?

    • Jessica Yoo

      You’ll still be able to use whichever DNS servers you like. We can verify valid records using commands like dig in order to validate requests to unblock mail ports. More information about using dig can be found via this link.

  7. Author Photo

    I am curious how do you plan to work this for setups where servers come up and down frequently but have a need to send email when done? Is this going to be an account wide approval or per machine approval?

    What is going to be the SLA for response on these requests?

  8. Author Photo

    I am an existing customer. If I understand correctly I can still provision a new server and not have to contact support to get it unblocked?

  9. Author Photo

    Oh cool. I’m sure people are going to be happy to reach out to support immediately after creating an account and waiting hours to actually have full access to the services they’ve paid for.

    Such a useless change that will undoubtedly be followed by more. How long until each Linode requires justification?

    • Jim Ackley

      Hi James! Between actively looking for tickets related to these SMTP restrictions and our 24/7 phone support, we’re able to grab most requests fairly quickly. And I can definitively say that we have no plans to require justification for each new Linode 🙂

  10. Author Photo

    Based on what I see in my servers logs, only one way to fight with spam and attack attempts originated from Linode subnets is to block traffic from them. There is no day without attempts: – – [05/Dec/2019:19:28:52 +0000] “GET /api/v1/pods HTTP/1.1” 403 341 “-” “Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36” – – [05/Dec/2019:23:46:37 +0000] “GET /msdn.cpp HTTP/1.1” 400 345 “-” “WinHTTP/1.1”

    • Author Photo

      Hey there — our Trust & Safety team has determined that the IP addresses you’re reporting are currently operated by security researchers, and that the associated traffic isn’t intended to be malicious.

      Apart from blocking traffic originating from us, we’d gladly pass blacklist requests for your own IP addresses on to our customers — just send the requests to us at along with the information you’ve posted here. We monitor this email 24/7, so you can also report any other malicious activity you see coming from our platform there and we’ll quickly investigate.

  11. Author Photo

    I feel that this is a good approach, however, those that do have an SMTP server might now know the best ways to fight spam.

    Perhaps it would help to have a linked document on best practices, or considerations to keep in mind, emphasising stuff like…

    – Establishing and maintaining a secure password policy for e-mail accounts (so passwords can not be ‘123456’ or ‘password’, and some other dumb ones)

    – Having an outgoing filter might avoid spam/malware distribution (ie. SpamAssassin, MailScanner, or cloud services like SpamExperts, MailChannels)

    – Preventing users from redirecting their inbox to free e-mail providers (or any at all) will also stop spam distribution. Most of these services provide POP/IMAP import which is by far superior to a forwarder

    – Enforcing SPF / DKIM on your domains, and outgoing SMTP server. This will make it harder for people to use your domains for phishing, but also will prevent your own server from sending e-mail thru domains you don’t own.

    – Setup your SMTP server to reject outgoing e-mail when it belongs to an e-mail address that you don’t own (ie. don’t allow your servers to send e-mail personifying someone else)

    – Always use SSL, everywhere, self-signed or free certificates are OK, but not recommended.

    • Author Photo

      Hi Emiliano!

      Those are all great points. Thank you for outlining them for people. Linode has a few different email server guides that walk the user through setting things up properly. In particular, the Configure Spam and Virus Protection section of the Running a Mail Server guide, which is linked in the post above. This section goes over a few of the things you’ve mentioned. I can definitely see how helpful it would be to have all of this information in one place. So, I’ve passed your suggestions along to our documentation team for consideration. ?

  12. Author Photo

    It would be better if Linode default whitelist certain well-known 3rd party SMTP gateways. For example “” for Amazon SES service.

    I mainly use Amazon SES for email because of reliability. After I moved my website to linode, I found that all the email can’t be send because Linode blocked my server connect to Amazon SES gateway. Now I have to open a ticket and wait for unblock, not a smooth experience overall.

    • Author Photo

      Hi Kam,

      I’m sorry to hear that you experienced some frustration with this process. We are constantly looking for ways to improve this procedure, and we really appreciate you sharing your thoughts with us. I can definitely understand the validity of your point, so, I’ve passed it along to our team for further consideration.

      Please, feel free to share any thoughts you may have about any of our services by sending an email to

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