MailMonitor: Inbox delivery optimization tools & services

A complete suite of deliverability tools & services makes it easy to get back in the inbox.

It is a free and open-source mail transfer agent that routes and delivers electronic mail. It is Wietse Venema's mail server that started life at IBM research as an alternative to the widely-used Sendmail program. Now at Google, Wietse continues to support it.

We offer one platform that covers all email-related needs in one place: testing, sending, and in-depth tracking to control how email infrastructure works and performs.

Litmus is a testing service for web and marketing professionals. It allows people to cross-browser test their websites, and test their email newsletters across a range of email clients and spam filters.

It is an open source IMAP and POP3 email server for Linux/UNIX-like systems, written with security primarily in mind. It is an excellent choice for both small and large installations. It's fast, simple to set up, requires no special administration and it uses very little memory.

Email on Acid is the most affordable, self-serve email testing platform in the world. We can help you maximize the success of your email marketing efforts by diagnosing and improving your renderability, deliverability, click-throughs and conversions.

It is an email testing tool for developers. You can configure your application to use MailHog for SMTP delivery. You can view messages in the web UI, or retrieve them with the JSON API.

It adds scheduled sending and the easiest, most integrated email reminders to Gmail, helping you reach Inbox Zero.

250ok is an email deliverability tools company that produces a Software‐as‐a‐Service (“SaaS”) platform to monitor and measure the deliverability of email networks. These networks consist of companies sending various forms of messages including marketing, transactional, share, and others from various platforms.

It runs a super simple SMTP server which catches any message sent to it to display in a web interface. It catches all mail and stores it for display. It shows HTML, Plain Text and Source version of messages, as applicable.

For the best HTML e-mail delivery results, CSS should be inline. This is a huge pain and a simple newsletter becomes un-managable very quickly. This script is the solution.

Automate email and SMS tests, like account verification and password resets, using any language or testing framework using the Mailosaur API. Stop email being delivered to customers using fake SMTP servers.

Mailinator is a disposable email service that allows QA departments to test with 1000's of inboxes.

It helps build lasting business relationships, right from your inbox. A sales engagement platform designed for sales professionals and account managers.

MailSlurp is an end-to-end email testing service. It has a web-app for managing your account and a REST API for sending and receiving emails from randomly generated email addresses.

Is an AI-driven multichannel outreach platform that reaches prospects where they're most active while keeping every message personal, timely, and effective.

It is an all-in-one tool for email deliverability to make your Email Channel Reliable. It raises your sender reputation by interacting with real people in any language and helps you to hit the inbox of your prospect. Full automation.

It automates end-to-end email tests with a powerful GraphQL API and unlimited private email addresses and inboxes, test new user signups, transactional emails, drip campaigns, deliverability, spam scores, etc.

It is an SMTP server designed to run in your dev/test environment, that is designed to catch any email you or your application is sending, and display it in a web interface instead of sending to real world.

It is an online service that helps you create email templates and test them on dozens different physical devices and applications.

Your transactional email should NOT trigger spam or marketing filters. Flute Mail plugs into your existing API provider to properly isolate segments, boost inbox rates, and safely store your transactional email data.

Pinpoint email issues before you hit "send". Secure your emails from malicious actors and ensure your email delivery to the inbox.

It is an Email testing and Email preview tool to test emails on several devices, screen sizes, and email clients. It checks your email for broken HTML, and accessibility issues, preview the email from the notification bar, displays the reading time of your email, and improves readability.

Disposable email and fake email capture for QA and development teams

Free email checker and email verification with 99.9% accuracy. Reduce bounces, protect sender reputation. 100 free email verification credits daily.

Free email verifier & checker to validate email addresses instantly. Reduce bounces and verify emails in real time.

Sidemail is an all-in-one email delivery platform for startups that makes sending emails simple. It has everything for delivering and managing emails – email API, transactional emails, email marketing and automation, contact management, no-code email editor, email templates, subscribe forms, and more. Perfect for teams & developers that want reliable deliverability without the bloat. We're based in the EU and GDPR compliant.

MTN Email Verifier is a high-performance tool for ensuring that your email communications reach the right inboxes every time. With the rise of email marketing and automated outreach, maintaining a clean list of deliverable email addresses is crucial. MTN Email Verifier combines syntax validation, domain checks, and server-level SMTP verification to deliver a reliable, real-time solution.

It helps new brands and startups build an audience while they focus on building a product

It is an easy way to manage your outgoing emails from your apps. From creating and sending your emails to monitoring and managing their stats, you can do really useful things with it without worried about time zone disaverage.

Send emails that don't end up in the spam folder. Find out if your email is likely to trigger spam filters. Run a free email spam and security test in less than one minute.

It offers a simple REST-based JSON API enabling you to thoroughly check and verify email addresses right at the point of entry into your system.

Protect your domain with Dmarclytics. Run free DMARC, SPF, and DKIM checks to stop spoofing, enhance email authentication, and improve deliverability with powerful monitoring tools.

Use AI to find prospects that need you, automatically craft personalized cold emails for each, and scale effortlessly

Aepto is an AI-powered domain monitoring platform built to give full visibility and control over domains spread across multiple providers. Instead of logging into separate registrar, hosting, and email dashboards, Aepto centralizes everything into one clean interface and continuously monitors domain health using public signals and AI analysis. Once a domain is added, Aepto automatically scans the registrar, hosting setup, email configuration, pricing, and renewal details—no APIs or integrations required. It monitors email deliverability, DNS records, website and subdomain uptime, content changes, and suspicious activity such as nameserver changes or lock status updates. When something goes wrong, Aepto alerts you early and clearly explains what happened and which provider to contact. Aepto also helps track domain expenses, visualize spending, assign ROI, organize domains into folders, and customize pricing and provider details when needed. Advanced features include AI-powered domain discovery, domain watch for tracking expiring domains you don’t own, distributed uptime monitoring, and customizable white-labeled status pages with incidents and maintenance updates. Designed for businesses, agencies, and teams that rely on domains for live websites, email, and APIs, Aepto focuses on proactive monitoring and clarity—so nothing breaks silently and small issues don’t turn into bigger problems.

Outreach Box is an AI-powered sales engagement, marketing automation and email outreach platform designed to help businesses find warm leads, scale outreach campaigns, and close more deals. With intelligent automation, unlimited email outreach, advanced deliverability, AI-generated personalized solution, and real-time campaign analytics, Outreach Box enables sales and marketing teams, agencies, and marketers to increase business reach and automate daily works for better output.

Ark is the AI first email API. Send transactional emails with native MCP support, sub-second delivery, and 99.9% deliverability.

It is an advanced MTA built to handle the most critical reliability, performance, security, and deliverability requirements.

It is a one stop email testing platform which helps improve the emails being sent from application and reduce the costs associated with email workflow testing.

It is an Email Tracking for Gmail and GSuite, adds the double check marks to your mail if it is read by recipient (Just like WhatsApp), Receives real-time pop-ups notification on your desktop when your emails are opened.

It is an E2E email testing platform. It allows you to receive emails with code and automate email flows. You get a unique subdomain and access to unlimited custom email addresses.

It is an all-in-one email deliverability platform to supercharge your email performance. Locate, solve, prevent email deliverability pitfalls, and become a credible sender for any ESP provider.