Broadband ISP YouFibre UK Set to Block Email Internet Port 25 from Friday

Internet service provider YouFibre, which is one of the main retail outlets for Netomnia’s growing national Fibre-to-the-Premises (FTTP) based broadband network, has informed customers that they intend to impose a block against internet traffic on Port 25 (SMTP) from Friday (16th January 2026).

Broadband ISPs usually try to steer clear of blocking internet connectivity and services if they can help it, although it should be said that port 25 has been blocked by various other providers over the years to help prevent email spam. The port was historically used for the Simple Mail Transfer Protocol (SMTP) relay between mail servers (i.e. sending emails), which is usually not encrypted.

However, these days it’s more common for email servers and systems to use Port 465 (legacy SMTPS), Port 587 or Port 2525 for the secure variant of SMTP (SMTPS), which will usually be encrypted using the SSL/TLS standards or similar methods.

Suffice to say that customers of YouFibre shouldn’t be too alarmed after the ISP emailed them this week to inform of the impending change (credits to one of our readers, Joe, for the tip), although there’s always a risk from the unintended consequences of such moves.

Copy of You Fibre’s Email

We are doing a security update on the YouFibre network

Dear XXXXXX,

As part of our regular updates to the security of our network, we are implementing a new security measure – the blocking of Port 25 (SMTP).

This change will take effect on Friday 16 January, 2026.

Why are we doing this?

Port 25 is traditionally used for sending emails via the Simple Mail Transfer Protocol (SMTP). Unfortunately, it is also commonly exploited by spammers and malicious actors to send spam and phishing emails, often from compromised computers within our network. By blocking Port 25, we will reduce Spam and Phishing Attacks.

What you need to know

Although this change won’t impact most of our users, those using Gmail, Outlook or other web based email will be unaffected, it may impact some of our customers, particularly those who operate their own mail servers or use email applications configured to send emails via Port 25.

Here is what you need to know:

1. Email Delivery via Port 25: If you are using an email client or service that relies on Port 25 to send emails, you will need to reconfigure it to use an alternative port. Common alternatives include Port 587 or Port 465, which are typically used for secure, authenticated email submission.

2. Support and Assistance: If you need help reconfiguring your email client or server, please contact your email provider.

How to change your email port settings

To avoid disruption in your email service, please follow these steps to change your port settings:

1. Open your email client settings.
2. Locate the outgoing server (SMTP) settings.
3. Change the port number from 25 to 587 or 465.
4. Ensure the “Use secure connection (SSL/TLS)” option is enabled.

For more information see our help article: Why Can’t I Send Emails on My Connection?

We believe this change will significantly enhance the security and efficiency of our network. Thank you for your understanding and cooperation as we implement this important security measure.

Best regards,

The YouFibre Network Team