Email Gateway software

Mailer To Go is a transactional email service. Applications send through SMTP or an HTTP API, from a domain verified with SPF and DKIM. It is also a Heroku add-on, so a Heroku app can read its SMTP credentials from config vars instead of running a mail server on a dyno.

https://mailertogo.com/

Read reviews of Mailer To Go

Amazon Simple Email Service (SES) is AWS's email platform for application and bulk mail. Applications send through SMTP or the AWS API, from identities you verify in the account. It processes bounces and complaints, and it lives in the same account as the rest of an AWS deployment.

https://aws.amazon.com/ses/

Read reviews of Amazon SES

SendGrid, part of Twilio, sends transactional and marketing email. Apps connect over SMTP or a web API, authenticate a sending domain, and use templates for receipts, alerts, and campaigns. The activity log shows which messages were delivered, deferred, or bounced.

https://sendgrid.com/

Read reviews of SendGrid

Mailgun is an email API for sending and receiving. It offers SMTP and HTTP APIs, inbound routes, and logs for accepted and failed messages. Teams use it for application mail such as password resets, notifications, and messages that an app needs to parse on the way in.

https://www.mailgun.com/

Read reviews of Mailgun

Postmark sends transactional email such as password resets, invoices, and welcome messages. It keeps that mail apart from bulk marketing, so a newsletter does not drag down the reputation of messages people are waiting for. Apps send through SMTP or an API, with templates and delivery tracking.

https://postmarkapp.com/

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Mailjet sends both the messages an application triggers and marketing campaigns to a list. Transactional mail goes out over SMTP or the API, and the same account can run newsletters on a separate stream. It includes templates, contact lists, and statistics for opens, clicks, and bounces.

https://www.mailjet.com/

Read reviews of Mailjet

An email gateway can sound like a piece of network hardware, but for most applications it is the service that takes the mail your software needs to send and delivers it to someone's inbox.

What is an email gateway?

An email gateway sits between your application and the public mail system. Your app hands it a message, usually over SMTP or an HTTP API, and the gateway handles the connection, the authentication, and the delivery.

These tools exist because an application server is a poor place to run a mail server. Shared addresses are easy to block, outbound mail ports are often closed, and one badly sent batch can get a domain treated as spam. A gateway sends from a maintained network, signs each message, and watches the reputation of the domain you use.

Most gateways ask you to prove you own the domain you send from. You publish DNS records so receiving servers can check that the message really came from you, and so a forged message that uses your domain is easier to reject. After that, password resets, receipts, invitations, and alerts go out through the gateway instead of from the application itself.

Dashboards show what was accepted, what bounced, and what people marked as spam. That record is how you notice a broken address, a bad template, or a sudden drop in delivery before users start telling you that mail never arrived.

What do email gateway solutions handle?

They accept mail from your application, queue it, and deliver it to inbox providers. They sign messages, process bounces and complaints, and slow a sudden spike so it does not look like abuse. Many also store a log of each message and keep transactional mail separate from bulk mail, because a newsletter and a password reset should not share a reputation.

Why use an email gateway?

The biggest reason is that the message arrives. A sign-in code that lands in spam is a broken product, and fixing that by maintaining your own mail servers is a job most teams do not want.

• Send application mail from your own domain
• Keep receipts and sign-in codes out of the spam folder
• See bounces and complaints without running a mail server

How to choose

Start with the mail you actually send. Transactional messages, such as receipts and sign-in codes, need to arrive quickly and from a clean reputation. Newsletters need list tools and a separate domain, so a marketing campaign cannot damage the mail people are waiting for. Check where the service sends from, whether you connect over SMTP or an API, and whether the price fits the volume you expect. Many teams use one gateway for application mail and another for marketing.