Email to Fax: The Open Source Way (No Monthly Fees)
You’ve got a fax number. Your counterpart has a fax machine. And you’ve got a Gmail account. The problem is these three things don’t naturally talk to each other — unless you’re paying eFax $25 a month to be the middleman.
There’s a better option: set up your own email-to-fax gateway using open source software. You control the server, you own the pipeline, and you pay per fax to your SIP carrier — not per month to a cloud vendor.
This guide covers how email-to-fax works technically, how ICTFax implements it, and how to send your first fax directly from Gmail or Outlook without touching a cloud subscription.
How Email-to-Fax Works (The Technical Picture)
The core idea is simple: your email server accepts a specially addressed email, strips the attachment, converts it to a fax signal, and routes it over your SIP trunk to the destination fax number.
Here’s what happens step by step:
- You send an email to
15551234567@fax.yourdomain.com - Your mail server (Postfix, Exim, etc.) receives it and routes it to the fax gateway
- The gateway strips the attachment (PDF, DOCX, image)
- The document is converted to a fax-compatible format (TIFF G3/G4)
- The fax is transmitted over SIP using T.38 protocol or G.711 passthrough
- You receive a delivery confirmation email back
Fax-to-email works the same way in reverse: incoming faxes are captured as TIFF or PDF files and delivered as email attachments to a configured address.
The whole stack runs on your own Linux server. No third-party cloud service touches your documents.
Why Businesses Choose Self-Hosted Email-to-Fax
The cost math is straightforward. A typical cloud email-to-fax service charges $20–$50/month, plus per-page fees once you exceed the plan limit. At 200 faxes per month, you’re easily spending $600+ per year.
Self-hosted with ICTFax:
- Server costs: $15–$40/month on a VPS (shared with other services)
- SIP trunking: $0.005–$0.01 per page — roughly $1–$2 per 200 faxes
- Software: free (open source)
Total annual cost for 200 faxes/month: ~$200–$500, depending on your server setup. No per-page fees after the first few hundred. At higher volumes, the savings compound quickly.
Beyond cost, regulated industries — healthcare, legal, financial — often prefer self-hosted because they control where the data lives. A document transmitted through a cloud fax service lives on that vendor’s servers. Self-hosted means your PHI or privileged documents never leave infrastructure you control.
ICTFax Email-to-Fax Architecture
ICTFax integrates with Postfix to create a complete email-to-fax gateway. The architecture has three components:
Mail transport agent (Postfix): Receives emails addressed to the fax domain. A transport rule routes fax-addressed emails to the ICTFax processing script instead of a mailbox.
ICTFax processing engine: Parses the email, extracts attachments, converts documents to fax format, and queues the transmission. Supports PDF, DOCX, DOC, XLSX, images (JPG, PNG, TIFF), and plain text.
FreeSWITCH/Asterisk fax engine: Handles the actual SIP fax transmission. ICTFax supports T.38 for reliable digital fax over IP and G.711 passthrough as fallback.
Delivery notifications are sent back to the sender’s email automatically: success with timestamp and page count, or failure with error code so you know whether to retry.
Setting Up Email-to-Fax in ICTFax
Here’s the high-level setup flow. Full step-by-step instructions are in the ICTFax installation guide.
Step 1: Install ICTFax
ICTFax runs on Ubuntu 20.04/22.04 or CentOS 7/8. The installer handles Asterisk, FreeSWITCH, Postfix, and the web application in one script. Minimum server requirements: 2 CPU cores, 2GB RAM, 20GB disk.
Step 2: Configure Your Fax Domain
Set up a subdomain like fax.yourdomain.com with an MX record pointing to your server. In ICTFax admin, configure the email-to-fax domain and map it to your SIP trunk.
Step 3: Configure Postfix Transport
Add a transport rule in Postfix that routes emails to the fax domain to ICTFax’s processing script. ICTFax provides the exact configuration lines in the admin panel.
Step 4: Configure a SIP Trunk
Add your SIP carrier credentials in ICTFax. The system supports any SIP provider that handles fax — Twilio, VoIP.ms, Bandwidth, or your own Asterisk gateway. Enable T.38 if your carrier supports it for best reliability.
Step 5: Send a Test Fax
Email a PDF to 15551234567@fax.yourdomain.com from any email client. ICTFax queues and transmits it. You’ll receive a delivery confirmation when it completes.
Supported Document Formats
ICTFax converts the following attachment types to fax format automatically:
- PDF (most common)
- Microsoft Word (DOCX, DOC)
- Microsoft Excel (XLSX, XLS) — converted page by page
- Images: TIFF, JPG, PNG, BMP
- Plain text (.txt) — formatted as monospace document
Multi-page PDFs are transmitted as multi-page faxes. No manual splitting needed.
Fax-to-Email: Receiving Faxes as PDF Attachments
Inbound fax works the same way in reverse. Configure a DID (Direct Inward Dialing) number with your SIP provider that routes to ICTFax. When a fax arrives:
- ICTFax answers the inbound call and detects fax tones
- The fax is received and converted to PDF
- The PDF is attached to an email and delivered to the configured mailbox
- The original TIFF is archived in ICTFax’s document library
You can route different inbound DID numbers to different email addresses — useful for organizations where each department has its own fax number. All inbound faxes are logged in the ICTFax web dashboard with timestamps, sender ID, and page count.
Integration with Email Clients
Because ICTFax uses standard SMTP, it works with any email client out of the box:
Gmail: Compose a new email, address it to faxnumber@fax.yourdomain.com, attach the document, send. No plugins needed.
Outlook: Same process. You can save the fax domain as a contact to make addressing faster.
Thunderbird: Works identically. Some users set up an address book group for frequently faxed numbers.
Programmatic sending: Because the interface is just SMTP, any application that can send email can send faxes. This is useful for automating fax transmission from line-of-business software that doesn’t have native fax support.
Security Considerations
Self-hosted email-to-fax gives you direct control over security at every layer:
- TLS in transit: Configure Postfix to enforce TLS for email delivery. The fax transmission itself uses T.38 over SIP, which can be secured with SRTP/TLS-SIP on supported carriers.
- Access control: Restrict which email addresses can send faxes by domain or user list in ICTFax’s admin panel. Prevent open relay abuse.
- Document retention: Configure how long sent and received fax documents are retained. For HIPAA compliance, set appropriate retention and implement access logging.
- Audit trail: ICTFax logs every fax transmission with timestamp, sender, recipient, page count, and delivery status.
ICTFax vs Cloud Email-to-Fax Services
| Feature | ICTFax (Self-Hosted) | eFax / RingCentral Fax |
|---|---|---|
| Monthly base fee | None (server cost only) | $20–$50+ |
| Per-page fees | None (SIP trunk rate) | Yes (after plan limit) |
| Data control | Full — your server | Vendor’s cloud |
| HIPAA compliance | Configurable by you | Requires premium plan + BAA |
| Email client compatibility | Any SMTP client | Any SMTP client |
| Setup complexity | Medium (1–3 hours) | Minutes |
| Custom fax domain | Yes | Limited/paid |
| Inbound fax routing | Full control | Basic routing |
Cloud services win on setup speed. Self-hosted wins on cost at volume, data control, and customization. For organizations sending more than 100 faxes per month, self-hosted pays off within 6–12 months.
Frequently Asked Questions
Can I use Gmail to send faxes without a cloud service?
Yes. With ICTFax and a properly configured email-to-fax domain, you send an email from Gmail to a fax number address and it transmits as a fax. No plugins or account changes needed on Gmail’s side.
What file formats can I fax from email?
ICTFax supports PDF, DOCX, DOC, XLSX, TIFF, JPG, PNG, and plain text. PDF is the most reliable for consistent formatting.
Is email-to-fax HIPAA compliant?
Self-hosted ICTFax can be configured for HIPAA compliance — you control encryption, data retention, and access logging. Cloud fax services require a Business Associate Agreement (BAA) and premium plans for compliance.
How fast is email-to-fax transmission?
Fax speed depends on the SIP carrier and the receiving fax machine. Standard T.38 fax transmits at 14.4 kbps — roughly 1 page per 30–60 seconds. Most transmissions complete within 2–3 minutes of sending the email.
Can multiple people send faxes from the same server?
Yes. ICTFax supports multi-user and multi-tenant setups. Each user can have their own outbound fax identity, and inbound DIDs can route to individual mailboxes.
Start Sending Faxes from Email Today
ICTFax is free to download and self-host. Your first fax costs a fraction of a cent in SIP charges. There’s no subscription, no per-page pricing plan, and no vendor controlling your document pipeline.
Download ICTFax and follow the installation guide to have email-to-fax running in an afternoon. Need to receive faxes by email too? The same setup handles both directions through the same email-to-fax and fax-to-email platform.