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.

shawfactor

Allows Buddypress group admins to send email and private messages to all group members from the group admin/manage section.
This plugin sends each message (PM or email) individually to each group member. And supports merge tags to personalise the message for each recipient.
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Love this plugin or want to help the LocalHero Project? Please consider <a href="https://lhero.org/portfolio/lh-buddypress-email-or-message-group-members/" rel="nofollow ugc">making a donation</a>.

LH Buddypress Email or Message Group Members

Allows Buddypress group Admins to send email and/or a private message to all group members .

Mass Messaging in BuddyPress vs LH Buddypress Email or Message Group Members