Kenny Zaron

This plugin allows for network administrators on WordPress multisite environments to send an email to users that 
they select based on the users’ roles in individual sites. For example, checking only “editors” will go through 
each active site and add anyone with the role of “editor” to your list of emails to send to.
To use the plugin after installation & activation, find Users / Mass Email in the network admin dashboard in your 
multisite install. Then, select the user types you wish to email and click on the button for “Load the List”. This 
will load the list of users to email. Then you may compose your email in the boxes provided and click the send 
button at the bottom of the screen. If all goes well you will be presented with a confirmation page indicating 
that your email was sent successfully.
This plugin is NOT intended for administrators to be sending unsolicited spam to their users. In fact, it was 
created with more formal environments in mind. One example would be a University setting where administrators 
of the network may need to notify students and faculty of potential downtime. With the plugin’s implementation 
I would imagine it would be a highly inefficient way of sending spam anyway.

Network Mass Email

Allows network admins to send a manually created notification email to all registered users based on user role.

Daniel Westermann-Clark

By default, WordPress network usernames cannot contain anything but lowercase letters and numbers. This plugin adds network options to let you include hyphens, underscores, or uppercase letters, if desired.
Furthermore, this plugin gives you the option to allow email addresses as usernames, or to allow all-numeric usernames (e.g. “1234”).
Finally, this plugin lets you override the minimum length for usernames (which defaults to four characters).
To follow updates to this plugin, visit:
https://danieltwc.com/
For help with this version, visit:
https://danieltwc.com/2011/network-username-restrictions-override-1-0/

Network Username Restrictions Override

Does what it says!

Override restrictions on WordPress network usernames.

Network Mass Email vs Network Username Restrictions Override