ElbowRobo

This plugin is for BuddyPress, it adds a dashboard menu and a tab in the messages section. Once you navigate into the messages section and click the “Mass Messaging” tab you have access to all the options which you chose in the dashboard.
Including mass messaging to:
<ul>
<li>Members</li>
<li>Members of Groups</li>
<li>Members of Blogs (Sites)</li>
</ul>
And:
<ul>
<li>Select all buttons to allow mass messaging to all members easily.</li>
</ul>
In this page you also see ‘subject’ and ‘description’ just like on the Buddypress compose page.

Mass Messaging in BuddyPress

This works great for what I need, thanks a lot!

Great plugin

Ever wanted to send a message to many people at once? Now you can, introducing - Mass Messaging.

alexhal

Allows Buddypress group Mods to send email to all group members from group admin/manage section. 
To enable E-mail members for mods simply put the code given below in your bp-groups-members-mail.php file in the end from wp-admin-> plugins-> editor :
<pre><code>add_filter('gmm_enable_for_mods','gmm_enabled_for_mods');
function gmm_enabled_for_mods(){
 return true;
}
</code></pre>
By default this “E-Mail Members” section is available to mods and admin . 
To change it a filter is available and you can change the access like this : 
To restrict this option to admins only 
 add_filter(‘bp_gmm_auhority’,function(){ 
 return ‘admin’; 
 });

Group Members Mail Plugin

I've done a quick test and it worked with no problems for unformatted email

Does what it says on the tin!

Allows Buddypress group Mods to send email to all group members .

Mass Messaging in BuddyPress vs Group Members Mail Plugin