Send large volumes of transactional and promotional email via SMTP
A free plan that is not a trial
Unlike basic trial plans, our free option provides a fully functional solution for both transactional and promotional emails.
- Transactional email
- Promotional email
The SMTP service for sending large volumes of email
When sending email messages is part of a business process, reliability is not a detail: every message must be delivered quickly, without ending up in spam.
Mailbox Relay is our SMTP relay service designed for the secure and high-performance sending of transactional emails (order confirmations, password recovery, internal monitoring…) and promotional emails (newsletters), from any application or platform.
Companies, developers, and professionals can continue using their usual tools (e-commerce platforms, CRMs, management software, or email marketing software) by simply connecting them to a reliable SMTP server built to handle large sending volumes.
Mailbox Relay is designed for
Web agencies
Managing newsletters and operational communications for their clients.
E-commerce and logistics
Sending order confirmations, promotions, and shipping notifications.
Marketers
Running promotional campaigns and newsletters through dedicated platforms.
Developers
Who want to easily integrate a reliable SMTP system into their software.
System integrators
Managing automatic email sending from management systems, printers, and business applications.
Management and monitoring systems
With automated email sending features.
We guarantee the best deliverability in four steps
Vetting
We apply strict customer and sender vetting to ensure security and integrity of service.
Double DKIM signature
Every message carries a double DKIM signature, so your reputation is independent of other platform users.
Sending Pool Intelligence
Senders are grouped into pools with other senders of the same reputation and message quality.
DMARC enforcement
Correct SPF, DKIM and From alignment, as the major mailbox providers require.
Vetting
The Vetting phase involves a strict control of customers and senders accessing the sending of messages, so that only trusted companies are granted access and use of the service. In this way, the integrity and security of the service is maintained.
Double DKIM signature
All emails sent via our platform are signed with a double DKIM signature as part of our authentication and reputation segmentation process.
The first signature is a standard element for all emails, and indicates to the recipient servers that the messages originate from the Mailbox infrastructure, immediately guaranteeing a high level of reputation for the messages sent.
Sending Pool Intelligence
Email messages are sent to recipients from our platform through a series of sending pools. Powered by machine learning, our Sender Intelligence system dynamically moves senders, grouping them with other senders that have the same level of reputation and message quality.
DMARC enforcement
DMARC Enforcement is our method to always guarantee SPF, DKIM and From correspondence with the sender domain, and consequently the correct DMARC alignment as required by the major mailbox providers.
Frequently asked questions
What is the difference between transactional and promotional emails?
Transactional emails are sent to a specific recipient to confirm an action or notify an event, such as order confirmations, sending invoices, password recovery.
Promotional emails are mass emails sent to many recipients for marketing purposes, such as promotional, sales or newsletter email campaigns.
Every user must indicate the message type they intend to send upon registration. This is crucial for our algorithm, which optimises sending by assigning the appropriate pool and calculating your reputation.
Is there a free plan?
Yes. Mailbox Relay has a free plan with 5,000 messages per month and no monthly fee. Unlike basic trial plans, it is a fully functional solution for both transactional and promotional emails.
Are there daily sending restrictions?
Generally, no, unless your account experiences an elevated rate of bounces or complaints, which may result in the imposition of a daily sending limit.
Reliable SMTP relay for transactional email
Send transactional and promo emails at top inbox rates, and earn margin on every message.