Harshit

Automatically subscribes your users so that they can be notified of any new content on the main site using one of the following plugins –
<ul>
<li><a href="https://premium.wpmudev.org/project/subscribe-by-email/" rel="nofollow ugc">WPMU’s Subscribe by Email plugin</a>.</li>
<li><a href="https://wordpress.org/plugins/email-subscribers/" rel="ugc">Email Subscribers & Newsletters</a>.</li>
</ul>
Note
<ul>
<li>In a multisite WordPress install, all the users creating new sites will automatically subscribed to the main site’s new content.</li>
<li>In a single WordPress installation, all users registering to the main site or getting added by other admins will be automatically subscribed to the main site’s new content.</li>
</ul>

Auto Subscribe Users

Helps us automatically subscribe all our new users being added to the multisite network in order send them notifications regarding new updates/important notifications regarding our service.



Works as described

Automatically subscribe your users, so that they can be notified of any new content on the site.

feedmeastraycat

WordPress removes the Update Services ability (Settings – Writing) when you create a network (aka enables WordPress MU/Multisite). 
Activate this plugin to get it back.
Note: This is only for WordPress setups with a network, aka multiple sites, aka multisites, 
aka WPMU in WordPress 3 and later.
This plugin might work with older WordPress MU sites. I haven’t tested it though. If you do, please 
let me know how it turned out.
<h3>Files</h3>
<ul>
<li>/activate-update-services/activate-update-services.php</li>
<li>/activate-update-services/README.txt</li>
</ul>

Activate Update Services

WordPress removes the Update Services ability when you create a network. Activate this plugin to get it back.

Auto Subscribe Users vs Activate Update Services