Acajoom is a newsletter and mailing list Joomla component, which enables site owner to stay connected with his / her customers and effectively communicate back to them without any hassle.
Acajoom component is available in two versions; free and commercial and can be obtained directly from developers-Joobi website or from Joomla.org site. Commercial version comparing to free offers more tools, even to get you started you'll be fine with free version.
Acajoom component automatically comes with subscription module, which will need to be enabled and assigned to left or right side bar depending on space availability as well as template structure.
Before enabling subscription, module site administrator will have to configure component first and then create lists as well as to upload users if available. During the component installation it will automatically build a list of all of the site users.
When component is all set up, then module can be assigned and assigned to sidebar as appropriate by template. Within module, administrator will be able to control display of subtraction lists, which will enable users to choose which list they want to sign up for.
When finding solution to your website, it is a good practice to know the site's purpose. This will help to select appropriate components for your site. Before considering components and plug-ins, site administrator needs to have a clear understanding how components will work together when installed. There are many joomla components that are already build to be connected with other Joomla components and some are not. Best approach is to find components that are build by one developer. This gives an assurance of site working better and upload time for visitors will be worse.
One more thing. When done configuring components and modules, uninstall all of the unused components, plugings and modules. Having to many active extensions installed may affect your site performance.