Fax emerged as a disruptive technology in the 1980s, providing businesses with the ability to safely transfer documents over existing telephony infrastructure. This level of security, accuracy, and speed was unmatched at the time—a letter or private courier simply couldn’t compete.

Fast forward to the present day, and traditional faxing is something of a business relic. It’s still common in a few particular industries but for most of us, the need for a fax machine is all but gone.

Voice over internet protocol (VoIP) faxing is a replacement technology designed to retain the reliability and security of faxing, all while leveraging IP infrastructure. But how does it keep your business communications safe? Let’s find out.

What is faxing over VoIP?

Faxing over your VoIP phone service is largely the same process as using a traditional fax machine. A document is copied by the machine and securely transmitted to the recipient. Internet fax will either use email messages or internet fax services to facilitate the one-to-one transfer of information, effectively mimicking the analog process that used traditional phone lines.

How does transmission over VoIP differ from traditional methods?

For the most part, the process is the same. The key differences lie in the way the data is transferred—digital signals in a VoIP environment instead of analog signals—and in the infrastructure required to support the process.

Is faxing still relevant in 2025?

As mentioned, faxing is not the global technology it was 30 years ago. For many organizations, the heavy emphasis on security isn’t relevant, and the additional steps needed over modern alternatives like email and instant messaging make it less useful.

Faxing is still useful in industries with strict regulations and compliance requirements, such as healthcare companies and legal firms.

When security is not recommended but demanded, faxing stands as one of the most effective methods of document transmission. Faxing over VoIP retains that level of security while bringing the technology into the digital age.

Benefits of fax over VoIP

Faxing over VoIP has several benefits when compared to telephony faxing. While some of the advantages will vary from industry to industry, the benefits outlined here are well worth the investment.

1. Leverages modern internet infrastructure to handle communications

While a fax machine stashed away in the corner of the office was once a common sight across businesses worldwide, the same can’t be said today. As demand for the process has diminished, so too has the available physical infrastructure to support it.

VoIP faxing sidesteps the issue entirely, instead relying on the computers and mobile devices every company will have alongside the global IP network. So whether you’re looking at how to streamline recruitment processes when handling personal information, or a quick way to get signatures on contracts, VoIP faxing can help.

2. Faster and more capable of handling large-scale faxing workloads

IP networks have continued to evolve since their launch, with modern networks capable of gigabit speeds and massive amounts of data transfer. In comparison, a PSTN network can transmit only up to 64kbps (kilobits per second). That means it’s roughly 15,000 times slower at transmitting an equivalent-sized file.

3. More time and cost-effective

VoIP faxing is vastly more cost-effective than telephony faxing. It doesn’t rely on expensive and aging physical equipment, and you don’t need to be wired up to the PSTN. Just as a softphone has replaced a physical deskphone, VoIP faxing is freeing up offices of unneeded equipment. Plus multiple people can also send faxes at once—so you’re not wasting your staff’s time as they wait for the machine to be free.

Furthermore, by leveraging the extensive IP network that spans the globe, there is a wider reach for faxes than even the well-established PSTN network. Internet subscriptions are a part of every company’s expenses, which means there will be little additional outlay in getting your digital fax system up and running.

Challenges of fax over VoIP

As useful and simple as faxing over VoIP is, there are certainly some challenges to be aware of.

1. Analog tasks in a digital environment are complex

While a VoIP to VoIP fax will be a digital-only affair, sending something between a traditional fax machine and a VoIP fax system is a completely different beast. Analog to digital conversion is no simple process and can lead to all manner of issues if mishandled.

Of course, the process is automated by the machines and VoIP system themselves, but problems can still happen. The analog-to-digital conversion process introduces additional failure points that other systems won’t have.

2. Shares infrastructure with potentially insecure devices

As the vast majority of VoIP fax tasks will be handled using a personal computer that’s part of a vast network of connected devices, it is important to have robust IT security at all times.

While there are several safeguards in place to ensure a secure fax process time after time, the presence of an infected machine creates a dangerous situation that can be hard to quantify. Even with end-to-end encryption in place, a single compromised device could lead to loss of data, interception of incoming faxes, and profound complications for your business.

3. Reliability is dependent upon network conditions

As VoIP faxing essentially relies on the same network as your other communications, any instability or loss of network performance will impact your ability to send and receive faxes.

Any form of packet loss or jitter in the network can cause havoc with the faxing process, which demands absolutely rock-solid network conditions to ensure a successful transfer. Your ability to fax will depend on how robust your VoIP connection is.

Understanding encryption and compliance for VoIP faxing

Encryption has been at the heart of fax technology since its inception. There have been many methods and protocols in place to ensure consistent encryption and security, though the two most notable are the T.30 and T.38 protocols. The T.30 protocol governs the rules and regulations of any transmission of documents over the PSTN (public switched telephone network) and governs all fax procedures as a result.

Numerous other protocols touch upon smaller and more specific aspects of data transfer, such as the T.4 and T.6 protocols used for image transfers, but they all fall within the purview of the T.30 protocol. With the switch to digital-first transfers, however, the T.30 protocol is not fit to effectively moderate the process. For this reason, the T.38 protocol has been established to achieve the same goal: safe and reliable fax transfers.

The T.38 protocol explained

Created in 1998, the T.38 protocol was designed as an answer to the aging T.30 protocol and as a way to leverage IP technology. Fundamentally, it can operate in two main ways—as the end-to-end point for a fax to be transferred using T.38 to T.38 protocol, or as a go-between for T.30 devices that want to use the VoIP network.

The protocol determines the bandwidth limits and compression of the files. It also mitigates the threat of packet loss by using repeat packet sends as new packets are sent to ensure the final file can be faithfully reconstructed..

Digital encryption explained

One of the biggest advantages of digital faxing over PSTN faxing is the security itself. Traditional analog methods use audio-based encryption to protect fax transmissions by converting the file into audio information before being converted back to the intended file at the recipient’s machine. This form of security is exploitable in itself, but it is the machines used that are equally at risk of being compromised.

While no technology can claim complete protection from nefarious deeds, the security features in place with the T.38 protocol and VoIP faxing are more robust than traditional methods. There are a few key security functions to take advantage of, some of which are shared with other IP-based communications:

  • 256-bit encryption. An extension of 128-bit encryption that uses a 256-bit long key as a form of passcode that needs to be broken to access the document. Given the vast number of possible keys, it is incredibly hard to attack it with brute force.
  • Secure sockets layer (SSL). This is a form of authentication that ensures parties are the intended sender and recipient within a transaction.
  • Transport layer security (TLS). The true successor to SSL, TLS is a scrambling form of encryption that protects documents during transmission through a three-stage process – encryption, authentication, and integrity check.

These security features work together to keep critical documents safe, making faxing over VoIP a safe and secure option.

The next steps

Faxing over VoIP is a forward-thinking approach to resolving your business faxing needs while moving with the trend of technology. For as long as key industries need secure data transfer pathways, faxing will stand out—and VoIP faxing is the next step in the process.

If you’re on the fence about building a VoIP fax system within your business, consider what infrastructure you have and what will be needed to start faxing. If you have a fleet of PCs and a stable and secure enterprise network connection, you’re almost all the way there. With the right software, and some training on how to fax from a computer, it’ll soon be something you can add to your stack of communication tools.

It might not become the mainstay method of communication, but when security is the primary concern it is hard to beat VoIP faxing.

FAQs about faxing over VoIP

Can I use a fax machine without a landline connection?

Yes. You can still use a physical fax machine to send and receive documents using an internet connection and an analog telephone adapter over VoIP.

Is it possible to fax from my email account?

Many popular email services can integrate with VoIP faxing systems to send and receive faxes within the inbox itself. The process will vary based on your VoIP service provider and email system of choice.

Is it safe to fax sensitive documents?

Faxing is ideally positioned to transfer confidential files thanks to numerous security features such as 256-bit encryption, secure sockets layer, and transport layer security.

Updated Jun 24, 2025