SMHS have implemented an Open Source plugin for the Thunderbird email client to support the new MMHS Headers over SMTP specification. A description of what they have done, screenshots and download information is available on the SMHS website. This is the first client implementation of “Registration of Military Message Handling System (MMHS) header fields for use in Internet Mail“ General background on MMHS over SMTP can be found in the Isode whitepaper ‘Military Messaging (MMHS) over SMTP’.

The SMHS Thunderbird plugin makes it easy to try out MMHS over SMTP capabilities. It also inter-operates with Isode’s M-Switch server implementation. All of the features can be mapped using extended MIXER to STANAG 4406, enabling STANAG 4406 MMHS header support with an SMTP client. The Primary Precedence header also controls M-Switch’s MTS Grade of Delivery (priority) that can be used in an SMTP only environment.

This plugin is a good demonstration that MMHS over SMTP can be easily added to an SMTP client, which will facilitate wider implementation and adoption of this approach.