What’s the Issue with Port 25 Getting Blocked?

February 9, 2023 / General Discussion

In this post, We are going to explain why port 25 blocked?

Description – Many providers have prohibited access to send data out on port 25 to prevent spam from entering their network, but as we all know, this port is essential for communicating with other external mail services. It also prohibits legitimate users from receiving mail.

CPanel allows you to modify the port Exim listens on, but you don’t have the option to send emails through other ports. Other remote servers are unable to configure the manner to accept mail on non-standard ports since they are not capable of doing so. This is why it is critical for port 25 to be operational for mail to function properly.

You can test this block by connecting to an external mail server with the cURL program. In this tutorial, I’ll demonstrate how to use the PortQuiz service to test connectivity via port 25.

The following is what you’ll see: On a working system

# curl portquiz.net:25
Port 25 test successful!

The error message on systems containing this block changes significantly depending on the specific version of the cURL tool, but the utility will stall for roughly 300 seconds before failing with an error that looks like this:

# curl portquiz.net:25
curl: (7) Failed to connect to portquiz.net port 25: Operation timed out
# curl portquiz.net:25
curl: (52) Empty reply from server

Check if there are any “DROP” rules in iptables. If there is an “ACCEPT” rule, that is typical and expected. If you have any external or network firewalls, make sure they’re all up to date:

# iptables -L -n | grep :25
ACCEPT tcp -- state NEW tcp dpt:25


Several providers’ documentation addresses this issue. In most circumstances, you’ll need to consult your hosting or Internet service provider’s documentation or contact their customer care. If your provider is unable to remove these restrictions, you will need to use a relay service.

Note: Most residential internet service providers block port 25, and there is no way to get the restriction lifted. To use a relay service, you'll need to upgrade to a commercial plan.

Some ISPs automatically block port 25 but are prepared to unblock it if asked. In these circumstances, you may need to contact their customer service department or look over their paperwork to discover what procedures they require. Please be aware that the port may be restricted again if the provider receives spam reports.

Please contact your cPanel account manager if you are a hosting provider with specific documentation you’d want to add to this list.

If the supplier refuses to give access, you must supply your bodHOST or relay for them to use. If the configuration is not provided by default, the provider might give any sort of information for the bodHOST.

bodHOST relays may slow down the mail-sending process. When your server confirms that a message has been successfully transmitted, the message is delivered to the appropriate receiver by your external relay. Your relay provider may have to deal with issues that develop at the relay level. Your relay provider may need to handle issues that arise at the relay level.

If your service provider refuses to unblock port 25 or give an alternative, you can read about how to send an email when your service provider blocks port 25.

We hope you now have a better understanding. Why port 25 blocked? If you continue to have issues with the above-mentioned protocol, please contact the bodHOST Team for support. 24×7

Learn more about changing the SSH port by visiting our informative guide. How Can you Change the SSH port.html

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