InterFAX vs Retarus Fax (2026): which should you pick?
As of Nov 13, 2026, InterFAX grades higher than Retarus Fax: 2.4 against 1.8 out of 4.0.
Checked Nov 12, 2026 and Nov 13, 2026 · graded Nov 12, 2026 and Nov 13, 2026 by ToolGPA
InterFAX grades higher on the free plan and features. They get the same grade on value for money, ease of use and platforms.
Price, platforms and features side by side. The table says where each price was read and when.
InterFAX
Cloud fax by subscription or prepaid credit, with REST and SOAP APIs
Retarus Fax
Enterprise cloud fax with Outlook, API and printer connections
Which one is for you
Pick InterFAX if
- Fits if you want to add fax to your own software through an API
- Works for healthcare and finance teams that need compliance statements
Look elsewhere if
- Skip it if you want a yearly rate, as prices are shown monthly only
- Tight if you want toll-free numbers or several lines, which need a custom quote
- Watch out: PCI DSS compliant outbound faxing costs an extra per-fax fee that isn't published
- Skip it if you fax twice a year from a home office, as the pitch is built for developers and IT teams
Pick Retarus Fax if
- Fits if you are a mid-size or large company moving fax into Outlook
- Works for teams that need fax tied to SAP or Epic
Look elsewhere if
- Skip it if you are an individual or small office, as it is aimed at larger companies
- Skip it if you want a price on the page, since none is published
- Not for you if you want a free trial, as none is listed
- Watch out: the starting page covers only the Microsoft 365 and Outlook option of a wider product line
How we grade them
| 2.4GPAInterFAXFair | 1.8GPARetarus FaxWeak | |
|---|---|---|
| Value for money | C$9.95 a month for 100 inbound and 100 outbound pages, matching the category's $9.95 middle. Extra pages are $0.09 each, and long pages are billed in six-second steps. | CNo prices are published; the site is built around scoping with a project team. |
| Free plan and trial | CA free trial on monthly plans, which the product page describes as 30 days of free credits. The listing doesn't say if a card is needed. | FNo free plan or trial is listed, so nothing can be tried without paying. |
| Features | BREST, SOAP and SMTP APIs, Gmail and Outlook sending, Salesforce and healthcare connectors, and SOC 2, ISO 27001 and HIPAA statements. The listing shows no gap in the fax job itself. | COutlook and Microsoft 365, several ways in, APIs and connectors, a web portal with tracking, global infrastructure and migration help. |
| Ease of use | CNo store rating on record. The pitch is built around developers and IT teams wiring fax into other software. | CNo rating on record. A project team scopes it and you connect Outlook or an API. |
| Platforms and integrations | BWeb admin, with REST, SOAP and SMTP APIs, code libraries on GitHub, and Epic, OncoEMR and Salesforce connectors. No phone or desktop app is listed. | BWeb and Windows with Microsoft 365, Outlook, Epic, SAP and Active Directory. |
| Best for | fax with an API and compliance papers | enterprise cloud fax with Outlook |
The GPA is the average of the five grades: an A is 4 points, an F is none. The full reasons are on each tool's page: InterFAX and Retarus Fax. How we grade
Where they differ
- InterFAX also covers workflow automation.
- Retarus Fax also covers reports.
At a glance
| InterFAX | Retarus Fax | |
|---|---|---|
| Pricing | Free trial | Paid |
| Starts at | $9.95 per month for 100 inbound and 100 outbound pages, billed monthly | Not published |
| Free plan | None | None |
| Free trial | Free trial on monthly plans; the product page offers 30 days of free credits | None listed |
| Web | ||
| Windows | ||
| Made by | Upland Software, Inc. | Retarus |
| Price read from | uplandsoftware.com | Not confirmed |
| Checked | Nov 12, 2026 | Nov 13, 2026 |
Worth knowing
InterFAX
- Subscription prices are shown monthly only; no annual rates are listed.
- Pages longer than one minute are charged in six-second increments at one-tenth of the per-page cost.
- Toll-free numbers, multiple lines and larger prepaid packages need a custom quote from sales.
- PCI DSS compliant outbound faxing costs an additional fee per fax; the fee is not published.
Retarus Fax
- No prices are published; the site is built around scoping with a project team.
- Positioned for mid-size to large enterprises, not individuals or small offices.
- The page used as the starting URL describes the Microsoft 365 and Outlook option of a wider product line.
Key features
InterFAX
- REST, SOAP and SMTP APIs
- Developers can add faxing to an application with REST, SOAP or SMTP APIs and GitHub libraries for Java, .NET, PHP, Ruby and more.
- Email and desktop integrations
- Send faxes from Gmail, Outlook or any email client over SMTP, and fax from inside Salesforce.
- Healthcare integrations
- Connectors are listed for Epic 2017 and later and for OncoEMR, with HIPAA and PHIPA alignment stated for inbound and outbound faxes.
- Compliance options
- The vendor lists SOC 2 audited, ISO 27001 accredited and HIPAA compliant, plus PCI DSS compliant outbound faxing for a small extra fee per fax.
- Web admin and worldwide servers
- A web admin screen monitors usage, and servers in several regions are offered for data sovereignty.
Retarus Fax
- Outlook and Microsoft 365
- An Outlook add-in and Active Directory synchronization let Microsoft 365 users send and receive fax and SMS without in-house infrastructure.
- Several ways in
- Fax can be used through a web browser, Outlook, multifunction printers or a Windows application.
- APIs and connectors
- REST and SMTP interfaces are offered, plus pre-built connectors for applications such as Epic and SAP.
- Web portal and tracking
- IT teams configure services in a web portal, with real-time reporting on the status of individual faxes.
- Global infrastructure
- The page cites six data centers worldwide, multiple carriers and certifications including SOC 1, SOC 2, ISO 27001 and HITRUST.
- Migration help
- A named project team handles scoping, migration from fax servers, and custom integrations.
Plans
InterFAX
Fax + 200$9.95
per month for 100 inbound and 100 outbound pages, billed monthly
Local fax number included, no setup fee or contract; $0.09 per additional page.
Fax + 500$22.95
per month for 250 inbound and 250 outbound pages, billed monthly
Local number included, no contract; $0.09 per additional page.
Fax + 1000$42.95
per month for 500 inbound and 500 outbound pages, billed monthly
Local number included, no contract; $0.08 per additional page.
CustomCustom
Built with sales: toll-free numbers, multiple lines, extra security options and data sovereignty at high volume.
Pre-paid Basic$10
one-time purchase of 91 pages at $0.11 per page
No monthly commitment or minimum. A $50 Level 1 package gives 500 pages at $0.10; larger packages come from sales.
Retarus Fax
Pricing could not be confirmed. See retarus.com.
Ways to pay less
InterFAX
- Other savings
Free developer program with free faxing to one number
InterFAX says its free Developer program includes API access, free faxing to one number and expert support.
Retarus Fax
No public discounts listed.
Common questions
Which is cheaper, InterFAX or Retarus Fax?
As of Nov 13, 2026, InterFAX starts at $9.95 per month for 100 inbound and 100 outbound pages, billed monthly, and Retarus Fax has no price we could confirm.
Which has a free plan, InterFAX or Retarus Fax?
As of Nov 13, 2026, neither InterFAX nor Retarus Fax has a free plan. InterFAX has a free trial.
Which platforms do InterFAX and Retarus Fax run on?
As of Nov 13, 2026, only Retarus Fax lists a Windows app. Both list a web app. A platform missing from a listing is one its maker's pages did not mention.
More comparisons
How this page was made
- The verdict at the top follows a fixed rule. When both tools are in the same category and either is in our top three for it, the verdict follows that ranking: the higher-placed tool is our pick. The top three weigh who each tool suits as well as its grades, so a pick can go against the GPA. Otherwise the page does not pick one and says which grades higher: the higher GPA first; on a tie, the one with a free plan, then the one that starts cheaper in dollars a month, counted the same way for both; if they are still level, what the choice depends on.
- The grades are our own, from each tool’s review or report card. The GPA is their average.
- Prices, plans and platforms come from each tool’s listing. The table above says where each price was read and when.
- The differences and the answers to the questions are worked out from those listings.