GreenArrow Email Software Documentation

Injecting Mail

Injection Methods

There are two methods for injecting messages into GreenArrow Engine - SimpleMH and Raw Injection. SimpleMH is easier to use and provides more features, so we recommend using it in most circumstances. Raw Injection predates SimpleMH and can be useful for legacy integrations.

Network Injection Protocols

GreenArrow Engine has a few network-based injection options:


This is the most commonly used protocol for network-based mail injection. SMTP clients can be authorized by injecting IP address or using SMTP AUTH (username/password based authentication).

HTTP Submission API

GreenArrow Engine provides an HTTP submission API. For applications where network bandwidth is a bottleneck, this API has the advantage of supporting gzip and deflate compression.


QMQP is less latency sensitive than SMTP. For single threaded injecting applications where network latency is the bottleneck, using QMQP instead of SMTP can increase injection speed.

More information is on the QMQP page.

QMQP Streaming Protocol

As an alternative to implementing a multi-threaded sending SMTP client library to send high volumes of mail, GreenArrow Engine supports the QMQP Streaming Protocol, which has many of the same performance benefits but is much easier to implement.

The QMQP Streaming Protocol is asynchronous. Messages that the client wishes to send are written (“streamed”) out to the server without waiting for any replies. This means that unlike SMTP and QMQP, a network round-trip latency is not required for each message sent.

More information is on the QMQP Streaming Protocol page.

Local Injection Options

When your injecting application is running on the same server as GreenArrow Engine, you have access to the same network-based injection options as remote injecting systems. You also have a few additional options, which are only available with local injection.

Copyright © 2012–2024 GreenArrow Email