DuoCircle

What DuoCircle is

DuoCircle LLC runs a family of specialized email products grouped under four headings: authenticate, protect, deliver and route. The home page says it has operated since 2014, counts more than 50,000 organizations as customers, and sums up its approach as "Email experts, not sales reps." For senders, the product that matters is Outbound SMTP, sold at outboundsmtp.com: an SMTP relay for application mail such as transactional messages, system notifications, receipts and password resets. The same deliver group holds a Developer Email API at unsent.dev for teams that want an HTTP API rather than SMTP, Inbox Placement Testing under the InboxIssue name, and Cold Email Outreach under the NuReply name.

The company's case for buying from one vendor is that an email problem is rarely one problem. A spoofed domain, the home page says, is an authentication gap, a delivery gap and a routing gap at the same time, and DuoCircle aims to diagnose it, fix the records, send the mail and route what comes back, with "One company, one SLA, one expert who stays on it until it's solved." Its overall pitch is about 90% of the category leader's capability at roughly half the price, and it promises to say so, and point elsewhere, when a customer genuinely needs the missing 10%.

Outbound SMTP

DuoCircle's product comparison page lists what Outbound SMTP covers: SMTP relay for application mail; a free tier of 1,000 emails per month with no credit card required; volume-based pricing beyond that; reputation, throttling and routing handled inside the platform; sub-account and multi-tenant support; and standard SMTP authentication, so there is no application rewrite and no proprietary SDK. DuoCircle's guide to SMTP providers adds DKIM signing with every plan, real-time reports and analytics, protection against virus attacks in case your network is compromised, TLS encryption, multiple ports for relay mail, and 24/7 email, chat and phone support.

Standard SMTP authentication means an application, server or device that already sends over SMTP can move to the relay by changing its settings. The home page's own example is a business whose office copiers stopped authenticating to Office 365 and could no longer send scan-to-email. It signed up for the free tier, the copiers came back online, and a few weeks later the IT team noticed that mail leaving the relay was properly SPF and DKIM aligned, which led to fixing a deliverability problem it had lived with for years.

DuoCircle is direct about the product's scope. Outbound SMTP has no marketing campaigns or templates, no SMS, voice or WhatsApp channels, and no large SDK matrix; for sending shaped around an HTTP API, the company points to unsent.dev. Senders whose traffic is purely marketing campaigns with templates and segmentation are told to look at marketing email products, and cold outreach with sequences and warm-up belongs with NuReply.

Pricing

The free tier covers 1,000 emails a month with no card, and the home page encourages customers to use it "as long as it works" and upgrade only when their needs outgrow it. DuoCircle's SMTP guide lists paid plans starting at $4 a month for 2,500 emails and $11 for 12,500, rising to $550 a month for one million emails, with a 30-day money-back guarantee. Current pricing sits on outboundsmtp.com; the company says pricing is published on its product sites with no quote-only gating. MSPs and value-added resellers can join an MSP partner program.

Authentication and deliverability tools

Several of DuoCircle's other products matter to anyone sending mail from their own domain. AutoSPF manages SPF records, flattening them when they break the 10-DNS-lookup limit. DMARC Report, which the company says is a G2 category leader in several regions, shows who is sending mail as your domain, with a free tier for one domain and volume-based pricing after that. Mail Flow Monitoring has been fully free since 2018, and BIMI hosting is available once a domain has a VMC. Inbox Placement Testing covers the delivery side.

The home page describes how customers tend to combine them. A team arrives at AutoSPF to fix an SPF record, then adds DMARC Report when it realizes it has no DMARC enforcement and does not know who is sending mail in its name. A Phishing Protection customer keeps catching the same impersonation at the gateway, finds its DMARC policy is at p=none and its SPF at softfail, and pushes toward enforcement until the impersonation rate drops.

The protect and route groups complete the portfolio: Phishing Protection with click-time URL inspection, BEC defense and impersonation detection; spam filtering; Verisend visual mail verification for M365; SpamSentinel for HCL Notes and Domino; alumni forwarding for universities; tenant migration for M365 and Workspace cutovers; email forwarding; Backup MX; and Message Replay for per-message recovery.

Trust, security and support

DuoCircle has held SOC 2 Type 2 since 2022, audited annually by Hancock Askew & Co under the AICPA Trust Services Criteria for security, availability, confidentiality and processing integrity. Prospects can read the publicly published Bonterms Mutual NDA before requesting the report. The company lists CSA STAR Registry entries for six services, offers a full HECVAT to higher-education customers on request, and publishes its posture at trust.duocircle.com. It reports 4.8 stars on G2 across hundreds of verified reviews.

Support is the company's main selling point. It promises 24/7 SLA support and a same-day response, and says the person on the call is the person who will solve the problem, with no SDR funnel and no multi-tier escalation queue. Because most enterprise customers prohibit logo use, DuoCircle offers reference calls with them instead; Arakÿta and eXp Realty are the named customers, and Arakÿta's chief executive calls DuoCircle "easy to work with and willing to make it happen."

Who it suits

Outbound SMTP suits IT teams, MSPs and small businesses that need a dependable SMTP relay for applications, in-house servers and office devices such as copiers and scanners, without adopting an SDK. The free tier covers light sending indefinitely, the paid plans start low, sub-accounts help MSPs that manage several clients, and the same vendor can take on SPF flattening, DMARC enforcement and inbound security when those problems surface.

It is built for transactional and system mail. Marketing campaigns and cold outreach fall outside it by DuoCircle's own account, and developers who want an HTTP API first will find that in unsent.dev instead.