Nylas
Billions of people. Trillions of connections. One API. The Nylas APIs power applications with email, calendar, and contacts sync from any inbox in the world. Only Nylas provides one API for 100% of email, calendar, and contacts integrations. Add missing information in contact records. Make warmer intros with the help of a connection graph. Compile data from each address book to create a unified data source. Straightforward, universal connectivity to lower your costs, save time, and increase developer productivity. Transform data into insights and personalize the user experience. Fuel innovation with unique customer intelligence. Automate digital processes to drive business growth. Streamline user workflows with powerful scheduling automation. Discover how organizations just like yours are driving engagement and increasing customer satisfaction with the Nylas APIs.
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Critical Impact
Critical Impact allows you to enhance and simplify your email marketing campaigns. Our tools let you effectively manage your email and SMS lists, send personalized and automated emails, along with text messages (SMS) for your marketing campaigns all at a competitive price model. Our subscriber scoring algorithms will mine your data to quickly identify those subscribers who are most likely to read your next email, consume additional emails, or make another purchase.
With our easy-to-use interface, you can schedule messages to send in minutes. Select your send options all on one page, and then prevent mistakes by seeing a confirmation of all your send details. Even A/B test your email across device screens – from phones to tablets to monitors.
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Sendmux
Sendmux gives AI agents their own inbox and a controlled way to send email. Each agent can receive messages, read threads, handle attachments, send replies, and react to new mail through signed webhooks or Server-Sent Events.
Teams can send through Gmail OAuth, Outlook OAuth, SMTP providers, or managed Amazon SES. Sendmux can spread sending across providers with weighted routing, sender-domain routing, health checks, failover, and quotas by second, minute, hour, or day.
Developers get Mailbox, Sending, and Management APIs, OpenAPI docs, SDKs, the sendmux CLI, MCP tools, and Sendmux Skills. The platform also covers tenant isolation, mailbox-scoped API keys, custom domains, logs, metrics, and usage-based pricing with no per-seat or per-mailbox fees.
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SMTP.com
Reliable SMTP relay and email delivery services. Powerful email delivery services that enable you to send and track high volume emails effortlessly. Integrate and start sending in minutes. All your transactional, email relay and email delivery needs under one roof. Whether you need a low-latency email delivery provider for your transactional emails, scalable infrastructure for high-volume sends or reliable backend solution for your marketing campaigns, SMTP is built to deliver. Reputation Defender is SMTP’s proprietary technology that uses big data to proactively monitor your email list health and safeguard your domain and IP reputation among ISPs by suppressing bad emails in your sends from hard and soft bounces. This ensures your delivery rates and inbox placement incrementally gets better over time.
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