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Port 25 Blocking

 Port 25 is the port or connection on your computer through which outgoing email must pass. Port 25 blocking prevents spammers from sending masses of unauthorized junk email.

Frontier blocks all  SMTP (Port 25) traffic over our network that is not sent through Frontier outgoing mail servers ( This only applies if you have a dynamic IP address. If you have Frontier Business Class High-Speed Internet (or SDSL) and a static IP address, your outgoing email will not be affected.

If this has affected you, please change your outgoing mail server to You might also have to configure your email program to authenticate to our outgoing mail server. To find out how to do this, see Enable SMTP Authentication.

Note: Some customers telecommuting from home may be unable to send email using their companies' email systems. For your own security, we suggest establishing a secure connection via an application, such as VPN, in order to utilize the outgoing mail server for your place of business.

Still need help? Call 1.800.239.4430 or Live Chat

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