AuthSMTP
AuthSMTP is a UK-based, bootstrapped SMTP email relay service founded in 2003 that enables e-commerce sites, developers, mailing list operators, and small businesses to send outgoing email reliably via authenticated SMTP, with annual subscriptions starting at $72/year.
- Company typePrivate
- Founded2003
- HeadquartersChester, United Kingdom
- Headcount—
- GTM typeB2B
- OfferingSoftware
What AuthSMTP does
AuthSMTP, operating under UK-incorporated parent GetOnline Ltd, is a single-product authenticated outgoing SMTP email relay service founded in 2003 and headquartered in the United Kingdom. The company provides a globally available SMTP relay infrastructure that enables customers — primarily e-commerce websites, mailing list operators, email application developers, mail server administrators, and small/home businesses — to send transactional and bulk email reliably without facing common issues such as ISP port blocking, relaying-denied errors, SMTP authentication failures, or blacklisting. Core technical capabilities include authenticated SMTP relay with username/password security, SSL/TLS encryption, multi-port access (25, 26, 80, 465, 587, 2525, 325) to bypass ISP restrictions, SPF/DKIM/DMARC support with per-domain DKIM key isolation, anti-virus scanning of outgoing mail, and dedicated IP address options. Infrastructure is custom-built with redundant systems, Tier-1 network connections, and round-the-clock monitoring, hosted on AWS (London region since March 2022) with additional US data center presence.
The business model is a self-serve SaaS subscription with annual billing: accounts start at $72/£55/€62 per year for up to 2,000 messages per month, with flexible instant upgrades through a web-based Control Panel. Distribution is fully self-serve via the authsmtp.com website, with PayPal handling all payment processing. The go-to-market motion is product-led growth — instant account creation, money-back guarantee on new accounts, and extensive free setup guides for 100+ email programs and devices drive low-friction organic acquisition, complemented by SEO-optimized knowledge base content. A RESTful API v2 (currently in beta) extends the product surface to developers and enterprise integrators, supporting programmatic message submission, account status, and quota history endpoints with JSON-based requests. The company has no disclosed external funding, no known headcount, and operates as a bootstrapped, founder-led business serving a long-tail of SMB customers globally.
AuthSMTP firmographics
Firmographics- Name
- AuthSMTP
- Legal name
- GetOnline Ltd
- Website
- https://authsmtp.com
- Company type
- Private
- Founded year
- 2003
- Operating status
- Operating
- Short description
- AuthSMTP is a UK-based, bootstrapped SMTP email relay service founded in 2003 that enables e-commerce sites, developers, mailing list operators, and small businesses to send outgoing email reliably via authenticated SMTP, with annual subscriptions starting at $72/year.
- Ownership category
- akta.pro rank
AuthSMTP industry classification
Industry- Product category
- SMTP Email Relay / Outbound Email Delivery Infrastructure
- NAICS
- Computing Infrastructure Providers, Data Processing, Web Hosting, and Related Services (518)
- SIC
- Services-Computer Programming, Data Processing, Etc. (7370)
- akta.pro primary industry
- Email Authentication & Domain Protection (DMARC/SPF/DKIM) (HDADAKAC)
- akta.pro secondary industry
- Email Data Loss Prevention & Encryption (HDADAKAD)
Keywords
Where AuthSMTP is headquartered
LocationHeadquarters
- HQ city
- Chester
- HQ country
- United Kingdom
- HQ region
- Europe
Offices2 records
Markets served
AuthSMTP business model
Business model- GTM type
- B2B
- Offering type
- Software
- Cost components
- Infrastructure, Technology or R&D, Operations, Personnel, Marketing or Sales
Revenue model
- SMTP Email Relay Subscription: Annual subscription-based service with tiered pricing based on monthly message and data quotas. Accounts start at $72/£55/€62 per year for up to 2000 messages per month. Upgrades available instantly via Control Panel. Dedicated IP addresses available at no additional cost subject to approval.
Pricing tiers
| Model | Billing | Price |
|---|---|---|
| Subscription | Annual | Starter Account - Up to 2000 messages per month |
Go-to-market motion1 record
Distribution channels3 records
Marketing channels4 records
AuthSMTP product offering
Product offeringCore offering
AuthSMTP is an authenticated outgoing SMTP email relay service that enables e-commerce websites, mailing lists, email applications, and individuals to send outbound email reliably. The service resolves common issues such as relaying denied errors, SMTP authentication failures, ISP port blocking, and blacklist problems by providing multi-port SMTP access (25, 26, 80, 465, 587, 2525, 325), SSL/TLS encryption, SPF/DKIM/DMARC authentication with per-domain DKIM keys, and built-in anti-virus scanning. Accounts are sold as annual subscriptions starting at $72/£55/€62 per year for up to 2,000 messages per month, with instant online setup and a money-back guarantee.
Product overview
AuthSMTP is a single-product SMTP relay service offered by GetOnline Ltd. Its core offering is an authenticated outgoing SMTP email relay service that solves common SMTP and email relay errors for e-commerce websites, mailing lists, and email applications. The service includes a web-based control panel for account and sending configuration, a RESTful API (v2) for programmatic message submission and account monitoring, virus scanning for outgoing mail, and email authentication support (SPF, DKIM, DMARC). Pricing is subscription-based starting from $72 per year with message and data quotas. The company operates globally with servers in the UK and US.
Differentiator
Problem solved
Functional benefit
Products and services
- AuthSMTP Outgoing SMTP Email Relay Service Authenticated outgoing SMTP email relay service for e-commerce websites, mailing lists, email applications, mail server administrators, and individual users. Supports SMTP authentication, SSL/TLS encryption, virus scanning, SPF/DKIM/DMARC authentication with per-domain DKIM keys, multiple SMTP ports (25, 26, 80, 465, 587, 2525, 325), and dedicated IP address options. Annual subscriptions start from $72/£55/€62 for up to 2,000 messages per month, with a money-back guarantee.
- AuthSMTP RESTful API v2 JSON-based RESTful API (v2 Beta) for programmatic message submission, account status reporting, and up to 12 months of quota history including bounce rate, spam complaints, and error counts. Supports HTTP BASIC, X-Credentials header, or request body authentication. Includes a sandbox mode and rate limits of 500 requests per 60 seconds per user/IP. Available at api.authsmtp.com/v2/ on port 443.
Companies that use AuthSMTP
Customer profileNamed customers3 records
Segments6 records
Ideal customer profiles4 records
AuthSMTP technology and API
TechnologyTechnology focussed Yes
API detail
- Has API
- Yes
- API docs
- API detail
Core technology
AI maturity
App detail
Feature11 records
AuthSMTP partnerships and signals
Strategic signalPartnerships
Two partnerships are on record, tiered core.
- Amazon Web Services (AWS)coreAWS provides cloud-based infrastructure hosting for AuthSMTP services. Infrastructure is hosted in London, UK data centers (effective March 25, 2022). AWS serves as the primary sub-processor for cloud infrastructure services.
- PayPalcorePayPal handles payment processing for all AuthSMTP transactions. Supports credit/debit cards, PayPal funds, and bank transfers. Processes payments in customer's local currency. Provides secure payment processing without exposing customer financial data to AuthSMTP.
Scale indicators4 records
Recent moves4 records
Expansion highlights4 records
AuthSMTP competitors and assessment
Company assessmentDirect peers
- Brevo (formerly Sendinblue): Brevo offers SMTP relay and transactional email alongside broader marketing automation and CRM features. It is a direct peer that competes for the SMB and developer segments AuthSMTP serves, often bundling SMTP into larger marketing suites.
- SendGrid (Twilio): SendGrid is a leading cloud-based email delivery platform offering SMTP relay and transactional/marketing email APIs. It is the most direct competitor to AuthSMTP in the authenticated outbound SMTP relay space, serving developers and businesses of all sizes.
- SMTP.com: SMTP.com is a dedicated outbound SMTP relay service offering deliverability tools, dedicated IP addresses, and authentication support. It is a focused, direct competitor in the SMTP relay category, comparable in size and target market to AuthSMTP.
- Mailjet: Mailjet provides SMTP relay and email APIs for transactional and marketing email, with real-time analytics and templating. It overlaps AuthSMTP on outbound SMTP relay, especially for European SMB and developer customers.
- SocketLabs: SocketLabs provides an SMTP relay service alongside an email API and delivery tools, targeting developers and mid-market senders. It competes directly with AuthSMTP on outbound authenticated SMTP, deliverability features, and dedicated IP offerings.
- Mailgun: Mailgun provides an SMTP relay service and email API for developers, with strong emphasis on transactional email delivery, validation, and inbox placement. It competes directly with AuthSMTP for developer and application-to-email use cases.
- Amazon Simple Email Service (SES): Amazon SES offers outbound SMTP relay and email sending infrastructure tightly integrated with the AWS ecosystem, supporting DKIM signing and dedicated IPs. It is a primary competitor, particularly for cloud-native and developer-driven customers.
- SparkPost: SparkPost is an email delivery platform with SMTP relay and APIs, focused on transactional and large-scale sending with advanced analytics. It directly overlaps AuthSMTP's developer and high-volume use cases with more enterprise-oriented positioning.
- Postmark: Postmark specializes in transactional email delivery via SMTP relay and API, with strong reputation management and fast delivery guarantees. It targets application developers and SaaS companies, closely overlapping AuthSMTP's core use cases.
Broad incumbents
- Dyn (Oracle): Oracle Dyn (formerly Oracle Email Delivery) offers enterprise-grade outbound SMTP and email delivery infrastructure as part of Oracle's broader cloud portfolio. It competes with AuthSMTP at the enterprise tier with deeper platform integration but similar core SMTP relay functionality.
Market position
Strengths5 records
Weaknesses5 records
Competitive moat5 records
Key risks6 records
Key highlights6 records
Customer concentration
AuthSMTP social profiles
Digital presenceAuthSMTP financial estimates
Financial estimateRevenue estimate
Valuation estimate
AuthSMTP leadership team
Management profileNumber of profiles
AuthSMTP funding detail
Funding detailFunding overview
Funding rounds
Investors
Funding detail is available on the Subscription and Enterprise plan.Contact sales →
AuthSMTP M&A and investment
M&A and investmentM&A
Investments
M&A and investment is available on the Subscription and Enterprise plan.Contact sales →
Frequently asked questions about AuthSMTP
What does AuthSMTP do?
AuthSMTP is an authenticated outgoing SMTP email relay service that enables e-commerce websites, mailing lists, email applications, and individuals to send outbound email reliably. The service resolves common issues such as relaying denied errors, SMTP authentication failures, ISP port blocking, and blacklist problems by providing multi-port SMTP access (25, 26, 80, 465, 587, 2525, 325), SSL/TLS encryption, SPF/DKIM/DMARC authentication with per-domain DKIM keys, and built-in anti-virus scanning. Accounts are sold as annual subscriptions starting at $72/£55/€62 per year for up to 2,000 messages per month, with instant online setup and a money-back guarantee.
Is AuthSMTP a public or private company?
AuthSMTP is a private company. It is classified as founder individual operated bootstrapped and is currently operating.
When was AuthSMTP founded?
AuthSMTP was founded in 2003.
Where is AuthSMTP based?
AuthSMTP is headquartered in Chester, United Kingdom, in the Europe region.
How does AuthSMTP make money?
One revenue line is on record: SMTP Email Relay Subscription.
Who are AuthSMTP's main competitors?
Direct peers on record are Brevo (formerly Sendinblue), SendGrid (Twilio), SMTP.com, Mailjet, SocketLabs, Mailgun, Amazon Simple Email Service (SES), SparkPost and Postmark. Dyn (Oracle) is listed as a broad incumbent.
Does AuthSMTP have an API?
Yes. AuthSMTP offers a RESTful API v2.0 (BETA) for message submission and account management. Available endpoints include: 'send' (assembles and relays messages), 'send_formatted' (accepts pre-assembled message headers/body), 'status' (returns account status including expiry, quota limits, and usage), and 'quota_history' (returns quota history for up to 12 months including message/data usage, bounce rate, spam complaints, and error counts). Authentication supports HTTP BASIC, request body fields (user_id/api_key), or X-Credentials header. The API is available at https://api.authsmtp.com/v2/ on port 443. Form URL encoded requests/responses are deprecated; JSON is the recommended format. A sandbox option allows testing without sending actual messages or consuming quota. Rate limits: 500 requests per 60 seconds per user/IP, 100 errors per 60 seconds per user/IP, 5 simultaneous connections per IP. PHP code examples are provided. A legacy v1 API provides account details and usage summary but does not support message sending. Developer documentation is at www.authsmtp.com/api/v2.
What industry is AuthSMTP in?
AuthSMTP's product category is SMTP Email Relay / Outbound Email Delivery Infrastructure. Its primary akta.pro industry code is HDADAKAC, Email Authentication & Domain Protection (DMARC/SPF/DKIM), with a secondary code of HDADAKAD, Email Data Loss Prevention & Encryption. Its NAICS code is 518 and its SIC code is 7370.