How to Send Email to a Fax Number

Email-to-fax services act as a bridge between email and the traditional fax network. When you hit send, the service converts your message and attached documents into fax protocol (usually T.30 or T.38), then transmits them over the phone network to the destination fax machine. The recipient receives a standard fax—they never see your email.

This guide covers the specific steps to email a fax number, how to format the recipient address correctly, what file types you can attach, and which services support email-to-fax.

How to Send an Email to a Fax Number

Sending an email to a fax number requires signing up for an email-to-fax service, then composing an email with the fax number formatted as the recipient address. Here’s how it works:

1. Sign up for an email-to-fax service (5 minutes): Most services offer free trials—Dropbox Fax gives you 30 days, RingCentral offers 7 days. If you only need to send one fax and don’t want a subscription, ThirtyFax lets you send up to 5 pages for free with no account required.
2. Get your account’s fax domain: Each service has its own domain. Dropbox Fax uses @hellofax.com, RingCentral uses @rcfax.com, Fax.Plus uses @fax.plus. Check your service’s help docs for the exact format.
3. Open your email client: Use Gmail, Outlook, Apple Mail, or any email app. The sending address must match your account email—email aliases aren’t supported.
4. Format the recipient address as [fax number]@[service domain]: Remove all spaces, dashes, and parentheses from the fax number. For a US number like (999) 555-1234, you’d send to 19995551234@hellofax.com. More on formatting below.
5. Attach your documents: Add PDF, Word, Excel, or image files. Most services support up to 10-20 attachments. Your files are automatically converted to fax format.
6. Add a subject line and body text (optional): The subject becomes the cover page title. The body becomes the cover page message. If you leave both blank, most services send just your attachments.
7. Send the email: Hit send like you would with any email. The service processes your fax in the background.
8. Wait for confirmation: You’ll receive a confirmation email within a few minutes indicating whether the fax was delivered successfully. Allow up to five minutes per page for graphics-heavy documents.

Formatting the Fax Number in Email

The recipient address must include the full fax number with country code, followed by the service domain. Here’s how to format it correctly:

• Include the country code: For US and Canadian numbers, prepend 1. For example, if the fax number is (212) 555-1234, format it as 12125551234@hellofax.com.
• Remove all formatting: Strip out spaces, dashes, parentheses, and dots. (999) 555-1234 becomes 9995551234.
• US number example: 19995551234@hellofax.com (1 + area code + number + service domain)
• International number example: For a UK number like 020 7946 0958, prepend 00 plus the country code: 00442079460958@hellofax.com (00 + 44 for UK + number)
• Service domain varies by provider: Dropbox Fax uses @hellofax.com, RingCentral uses @rcfax.com, Fax.Plus uses @fax.plus. Check your service’s documentation for the exact format—it’s not universal.

Attaching Documents to Email to Fax

Email-to-fax services automatically convert your attachments to fax format (usually TIFF or PDF rendered at 204x196 DPI). Here’s what you can attach:

• PDF (most reliable): Supported by all services. PDFs preserve formatting best and rarely cause transmission issues.
• Microsoft Word and Excel: DOC, DOCX, XLS, and XLSX files work, but complex formatting may not survive conversion perfectly.
• Images: JPG, PNG, GIF, and TIFF are widely supported. High-resolution images increase transmission time.
• File size limits: Most services cap individual files at 20-50 MB. Dropbox Fax allows up to 40 MB per document, RingCentral caps combined attachments at 50 MB.
• Page count limits: Expect a cap around 200-250 pages per transmission. Sending more pages requires splitting into multiple faxes.
• Multiple attachments: You can attach multiple files. They’ll be combined into a single fax in the order you attached them.

Pro tip: Remove image-heavy email signatures before sending—graphics in signatures can cause processing failures. Also avoid special characters like ampersands in attachment file names.

Email-to-Fax Service Options

Several services support email-to-fax, each with different pricing and features. Here’s how they compare:

If you send faxes regularly, Dropbox Fax or Fax.Plus offer the best balance of features and price. RingCentral makes sense if you’re already using their communications platform. For one-off faxing, ThirtyFax is the fastest option—no subscription, no account, just send.

Written by

Bernard Bado

I created ThirtyFax after needing to send a single fax and refusing to pay for a monthly subscription to do it. I write here about faxing, document workflows, and the surprisingly stubborn role fax still plays in modern business.

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