The basic process: email address format and what happens next

To send a fax by email, you compose a message to a special fax-to-email address instead of a regular email address. That address follows a pattern: the fax number, then an @ symbol, then the fax service's domain. For example, if you use eFax, a fax number like 555-123-4567 becomes 5551234567@efax.com. The service converts your email into a fax and sends it to the recipient's fax machine.

The recipient receives a printed fax on their end, just as if you had sent it from a traditional fax machine. They do not receive an email. From their perspective, the fax came from a fax machine — they see a fax header with your name and number, not an email address.

The time it takes varies. Most services deliver within a few minutes during business hours. Some charge per fax; others include a set number of faxes in a monthly plan. A few services offer a limited number of free faxes per month before charging kicks in.

Key Takeaways

  • You send an email to a fax-formatted address (the fax number plus the service's domain), and the service converts it to a fax and delivers it to the recipient's fax machine.
  • The recipient sees a printed fax with a header showing your name and fax number, not an email message.
  • Common services include eFax, FaxZero, and Google Fax, each with different pricing and free fax limits.
  • Attachments must be in formats the service accepts — usually PDF, Word, or image files — and file size limits explore.
  • You need the recipient's fax number and, for some services, a fax number of your own to display on the fax header.

What you need before you start

You need the recipient's fax number. This is the phone number of their fax machine, not an email address. If you are sending to a business, their fax number is usually on their website or letterhead. If you are sending to a government office or healthcare provider, call ahead to confirm the fax number — fax numbers change, and sending to the wrong number means the document goes nowhere.

You also need to know which fax service you are using or plan to sign up for. Different services use different domain names in the fax address. eFax uses @efax.com. FaxZero uses @faxzero.com. Google Fax (through Google Voice) uses a different setup entirely. The service you choose determines the exact format of the address you send to.

Some services require you to have your own fax number, which they assign when you sign up. This number appears on the fax header so the recipient knows who sent it and can call you back if needed. Other services let you send without owning a fax number, but the recipient may see a generic or missing sender number.

Step-by-step: composing and sending the email

Open your regular email account — Gmail, Outlook, Yahoo, or whatever you use daily. Create a new message. In the "To" field, type the fax address in the correct format for your service. For eFax, that is the ten-digit fax number with no dashes or spaces, followed by @efax.com. For FaxZero, it is the same number format with @faxzero.com.

Type a subject line if you want one — some services include it on the fax header, others ignore it. Keep the message body short or leave it blank; the fax service will send what you type, but most faxes are documents, not text messages. Attach the file you want to fax. Use PDF format when possible, because it preserves formatting across different machines. Word documents, JPG images, and PNG files usually work too. Check your service's documentation for the full list of accepted formats.

Verify the file size. Most services cap attachments at 10 to 25 MB per fax. A typical document is well under that limit, but a scanned multi-page document or a photo-heavy file might exceed it. If your file is too large, compress it or split it into multiple faxes. Then send the email as you normally would.

What happens after you hit send

The fax service receives your email, processes the attachment, and converts it to fax format. This usually takes a few seconds to a few minutes. The service then dials the recipient's fax number and transmits the document. If the line is busy or the fax machine is offline, the service typically retries automatically — usually three to five times over several hours.

You will receive a confirmation email from the fax service saying whether the fax was delivered or failed. If it failed, the email will tell you why: the number was invalid, the fax machine was busy, or the recipient's fax was out of paper or offline. You can then resend or troubleshoot.

The recipient sees a printed fax with a header page showing your name, your fax number, the date and time, and the number of pages. The header format depends on the service and the recipient's fax machine, but it always includes these basics. The recipient does not see your email address or know that you sent it via email.

Common services and how they differ

eFax is one of the oldest fax-by-email services. It assigns you a fax number, charges a monthly fee (usually $10 to $20), and includes a set number of outgoing faxes per month. You can also receive faxes to that number, and they arrive in your email inbox. The service works from any email account.

FaxZero offers free faxes within limits — typically three free faxes per day to the US and Canada, with a watermark on the cover page. Paid plans remove the watermark and increase limits. It does not assign you a fax number, so the recipient may see a generic sender number or none at all.

Google Fax (through Google Voice) lets you send faxes from your Google account if you have a Google Voice number. You upload a document to Google Drive, open it, and use the "Print" function to send it as a fax. This works only if you already use Google Voice and have a number assigned.

Other services like HelloFax, Interfax, and RingCentral exist, each with different pricing and features. Some are designed for businesses and include features like fax scheduling or bulk sending. For occasional personal use, FaxZero or a basic eFax plan usually covers your needs.

Troubleshooting when a fax does not go through

If you receive a failure notice, the most common reason is a wrong fax number. Double-check the number against the source where you found it. Fax numbers are ten digits in the US; if you have fewer or more, it is wrong. Make sure you did not accidentally include dashes, spaces, or parentheses — the service needs just the digits.

The second most common reason is that the recipient's fax machine was offline, out of paper, or the line was busy. Most services retry automatically, so wait an hour or two and check your confirmation email again. If it still shows failed, try sending again during business hours when the machine is more likely to be staffed and ready.

If your file did not attach or the service rejected it, check the file format and size. Convert the file to PDF if it is in another format. If it is a scanned document, make sure the scan is readable — a blurry or upside-down scan may cause the fax to fail or arrive unreadable. If the file is very large, split it into two faxes.

Cost and free options

FaxZero is free for up to three faxes per day, with a watermark on the cover page. Beyond that, you pay per fax or upgrade to a paid plan. eFax charges monthly, usually between $10 and $20, depending on how many faxes you need to send and receive. Google Fax is free if you already have a Google Voice number, but setting up Google Voice may require a phone number.

If you send faxes rarely, FaxZero's free tier or a pay-per-fax service makes sense. If you send several faxes a month, a monthly plan like eFax becomes cheaper per fax. Some services also offer a trial period — usually 30 days free — so you can test the service before paying.

Frequently Asked Questions

Can I send a fax to an international number?

Most services support international faxes, but the cost is higher than domestic faxes. You need the full international number, including the country code (for example, +44 for the UK). Check your service's pricing page to see which countries are supported and what the per-fax cost is.

What if I do not have a fax number to display on the fax header?

Services like FaxZero let you send without owning a fax number. The recipient will see a generic or missing sender number on the fax header. If the recipient needs to call you back, they will have to contact you another way. For official documents, having a fax number to display is usually better.

Can I send a fax from my phone?

Yes, if your phone has email access. Compose an email on your phone, attach the document, and send it to the fax address just as you would from a computer. Some fax services also have mobile apps that let you take a photo of a document and send it as a fax directly.

How long does a fax take to arrive?

Most faxes arrive within a few minutes during business hours. The time depends on the recipient's fax machine, the file size, and the service's queue. If a fax fails on the first try, the service retries automatically, which can add an hour or more to the total time.

Is faxing by email find?

Email itself is not encrypted by default, so the email containing your document travels over the internet in plain text unless your email provider uses encryption. Once the fax service receives it, the document is converted and sent as a fax. If you are sending sensitive information, ask your service whether it offers encryption or find transmission options.