As the project owner you can decide which mail types are available for users on your project.
Project roles ensure each organization only has access to use the types and statuses that are specific to their job. This means they cannot accidentally use the wrong mail or doc type.
Users in your organization can also manage their own mail types, but you can prevent them from changing this setting.
Log into Aconex and click on Setup in the Menu.
Under Project, click on Project Settings.
Click Mail/Documents Role Settings.
Find the organization you want to update mail types for, and click the role that's ticked against them.
In this example I want to give more mail types to the Aconex organization, so I've clicked the Consultant role.
Find the mail type you want to add, and click on it in the list.
Click the right-pointing arrows to add the mail type to the role.
Click OK to save your changes. The mail type will now be available to use for organizations assigned to that role.