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Best Practices

The Dangers of Open Email Servers

By Ciara Noonan | 2 minute read

It is impossible to completely secure a server that is exposed to the internet. Cybercriminals, who are always looking for ways to send as much spam as possible, seek to exploit any entrypoint. An open email server is basically an invitation for them to hack in and use the vulnerable network to send out massive amounts of spam.

These attacks can also be used to steal identities, especially within corporate networks. A recent variant of the cutwail botnet specializes in using stolen credentials and spoofing users to steal employee identities, request wire transfers, and send out corporately authenticated spam.

Cutwail botnets are not a new threat, however their behaviour has evolved into the bot swamping servers and attempting to establish as many connections as it can. This ties up all the TCP sockets so they’re unable to handle verified email. Targeted systems have no choice but to severely restrict connections from compromised networks, which means that legitimate mail from those networks may be delayed or rejected.

You can do two things to maintain outbound email deliverability:

  1. Secure your servers against attack.
  2. Limit the damage that can be done if a botnet DOES get unauthorized relay access through a compromised account.

On a small network, it may be practical to limit which servers can deliver mail to the internet. But for web hosts that manage numerous email delivery mechanisms, this may not be feasible. Which is where MailChannels come in. Our solutions help you do both things to keep outbound email traffic spam-free and flowing.

Web hosts can count on MailChannels for:

  • Safe IPs – no blacklisting
    Our innovative technology ensures your servers remain safe from spam that could harm your IP reputation.
  • Compromised account alerts
    Our console lets you know when an account in your network is trying to send spam so that you can locate the compromised account and shut it down.

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