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To setup routing to a project by group membership, through the JEMH Configuration Screen edit the Project Mapping Settings, showing the following:
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Add a new Project Mapping
Clicking 'New Project Mapping' will present you with the mapping screen: 
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Fill in (at minimum) the Project key, other settings as required.
Note, you are unable to add Project/group mappings at this time. SAVE mapping first by clicking submit.
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Adding group mappings
Once saved, edit again, to see new options:
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One or more groups can now be added (comma separated). Any incoming mail picked up by this profile, associated with a JIRA user within these groups, will be routed to the given project.
Setup is complete:
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Multiple group mappings?
When multiple mappings are defined, they will all be tried until one succeeds, if at all.
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