The basic method: email-to-fax gateways

You send a fax through email by using an email-to-fax gateway — a service that converts your email message and attachments into a fax and delivers it to a standard fax machine. You address the email to a special fax number (formatted as an email address), attach your document, and the gateway handles the rest. The recipient receives it on their fax machine exactly as if you had sent it from a fax device.

Most gateways work the same way: you compose an email, put the recipient's fax number in a specific format in the "To" field, attach a PDF or image file, and send. The gateway converts that attachment to fax format and dials the number. No special software or hardware is required on your end — just email and a document file.

The recipient does not need email or any special setup. They receive the fax on their existing fax machine. This makes email-to-fax useful when you need to reach someone who still uses fax but you prefer to work from your computer.

Key Takeaways

  • Email-to-fax gateways let you send faxes from your email account by addressing the email to a specially formatted fax number.
  • Your document must be attached as a PDF, image file, or other format the gateway accepts — plain text in the email body usually does not fax.
  • The recipient gets the fax on their standard fax machine; they do not receive an email or need any special technology.
  • Some gateways are free but limit the number of pages per month, while paid services offer unlimited sending and better delivery confirmation.
  • The fax number format varies by service — some use fax@[number].efax.com, others use different patterns — so check your gateway's instructions.

How to format the fax number in your email

The exact format depends on which gateway you use, but the pattern is always: the fax number, an @ symbol, and the gateway's domain. For example, if you are using eFax and sending to fax number 555-123-4567, you might address the email to 5551234567@efax.com. Some gateways want the number with dashes, some without; some add a prefix or use a different domain entirely.

Before you send your first fax, check your gateway's website or documentation for the correct format. Entering the number wrong means the email bounces back or goes to the wrong place. Most gateways show you the format clearly on their setup page or in a help article.

Put nothing else in the "To" field — no other email addresses, no notes. The entire field should contain only the formatted fax number. If you need to send the same fax to multiple fax numbers, you may need to send separate emails, depending on the gateway. Some allow multiple recipients in the "To" field; others do not.

Preparing your document for faxing

Save your document as a PDF or image file (JPG, PNG, or TIFF). Fax gateways do not fax Microsoft Word documents, Excel spreadsheets, or other office formats directly — they need a file format that represents the document as a picture of the page. If your document is already in Word, use "Save As" and choose PDF. If it is a paper document, scan it to PDF or take a clear photo and save it as a JPG.

Keep file size reasonable. Most gateways accept files up to 10 to 25 MB, but smaller is better for faster transmission. A typical single-page PDF is under 1 MB. If you have a large document, consider splitting it into multiple emails or compressing the file before attaching.

Attach the file to your email as you normally would. The file name does not matter, but a clear name like "Invoice_2024.pdf" helps you keep track of what you sent. Do not put the document content in the email body — the gateway faxes only the attachment, not the message text.

Free versus paid email-to-fax services

Free gateways like Fax.plus, Faxburner, and some offerings from major email providers let you send a limited number of pages per month at no cost. These work well if you fax occasionally — perhaps a few documents a month. The trade-off is that you may see ads, get slower delivery, or have less detailed confirmation that the fax went through.

Paid services like eFax, MyFax, and Fax.com charge monthly fees (typically $10 to $30) and offer unlimited sending, better delivery reports, and the ability to receive faxes through email as well. If you fax regularly or need to know for certain that a fax was delivered, paid is worth the cost. Many paid services also let you store faxes in the cloud and search through your fax history.

Some services charge per fax rather than a monthly fee. This works if you fax very rarely — you pay only when you send. Check the pricing page of any service you are considering to see whether monthly, per-fax, or free-with-limits fits your situation.

Confirming your fax was delivered

After you send the email, the gateway processes it and attempts to dial the fax number. You should receive a confirmation email from the gateway within a few minutes to an hour, telling you whether the fax went through. Read this confirmation carefully — it will say "delivered," "failed," or sometimes give a specific reason like "busy signal" or "no answer."

If the fax failed, the confirmation usually tells you why. A busy signal or no answer means you can try again later. An invalid number means you entered the fax number wrong. Some gateways automatically retry failed faxes a few times before giving up.

Free services may not send detailed confirmations — you might get only a straightforward "sent" message. Paid services usually give you a delivery report with the time sent, number of pages, and whether the receiving fax machine accepted it. If you need proof that a fax was delivered, use a paid service or ask the recipient to confirm they received it.

Common problems and how to fix them

The most common issue is an incorrect fax number format. If your email bounces back when ready with an error, check the format against your gateway's instructions. A single wrong digit or missing symbol will cause failure. Some gateways are picky about dashes and spaces; others ignore them. When in doubt, try the number without any dashes or spaces.

If the fax fails to deliver but the format is correct, the receiving fax machine may be offline, out of paper, or not answering. Try sending again in a few minutes or a few hours. If it fails repeatedly, call the recipient to confirm their fax number is correct and their machine is working.

If you attached a file but the gateway says it cannot process it, the file format may not be supported. Convert the file to PDF and try again. If the file is very large, compress it or split the document into smaller pieces and send multiple faxes.

Receiving faxes through email

Many email-to-fax services also let you receive faxes through email. When someone sends a fax to your gateway's fax number, the service converts it to a PDF and emails it to you. This means you have one inbox for both email and fax — no separate fax machine needed.

To set this up, the service gives you a dedicated fax number. You share this number with people who need to fax you. When they fax that number, you get an email with the fax as an attachment. Paid services usually include this feature; free services may limit how many incoming faxes you can receive per month.

Receiving faxes this way is convenient if you work mostly from email and want to avoid managing a physical fax machine. The fax arrives in your email inbox like any other message, and you can forward it, print it, or save it to your computer.

Frequently Asked Questions

Can I fax a document that is already a photo on my phone?

Yes. Save the photo to your computer, then attach it to your email as you would any other file. Make sure the photo is clear and shows the entire document. You can also use a scanning app on your phone to create a PDF and email that PDF to yourself, then attach it to your fax email.

What if the fax number has an extension?

Most email-to-fax gateways do not support extensions. Fax machines do not recognize extensions the way phone systems do. If the fax number has an extension, call the company and ask for the direct fax line that does not require an extension, or ask them to set up their fax machine to accept calls to that extension automatically.

Can I send a fax internationally?

Yes, but check your gateway's pricing first. International faxes usually cost more per page than domestic ones, or may not be supported at all depending on the destination country. Most paid services support international faxing; free services often do not. Enter the fax number with the country code (for example, +44 for the United Kingdom) in the format your gateway specifies.

Do I need to use my real email address to send a fax?

Yes. The gateway needs a valid email address to send you the delivery confirmation. Use the email account you set up with the gateway service. You cannot send a fax anonymously or from a fake email address.

What happens if I send a fax to the wrong number?

The fax goes to whoever owns that fax number. If you realize the mistake before the confirmation arrives, there is nothing you can do — the fax has already been sent. If you catch it right after, contact your gateway's support to see if they can intercept it, though this is rarely possible. For sensitive documents, always double-check the fax number before you send.