quan_flo

If there is a user (or a bot) that signed up at your site this user can start to send messages to every other user. 
I had some negative experiences with this and so I wrote a module that should help to block such a spam.
Buddypress Messages Spam Blocker introduces some restrictions to your users:
<ul>
<li>New users can send messages only 24h after their registration, so you’ll have time if bot registrations have to be removed manually (modify this value using filter ‘buddypress_messages_spamblocker_newMembersWaitingPeriod’)</li>
</ul>
Their are also some more restrictions for mass mailings (mails that are sent to “friends” of the contact list are not included in this calculation):
<ul>
<li>Users can send 6 messages maximum in 5 minutes (modify this value using filter ‘buddypress_messages_spamblocker_5m’)</li>
<li>Users can send 10 messages maximum in 10 minutes (modify this value using filter ‘buddypress_messages_spamblocker_10m’)</li>
<li>Users can send 20 messages maximum in 30 minutes (modify this value using filter ‘buddypress_messages_spamblocker_30m’)</li>
<li>Users can send 30 messages maximum in 60 minutes (modify this value using filter ‘buddypress_messages_spamblocker_60m’)</li>
<li>Users can send 35 messages maximum in 12 hours (modify this value using filter ‘buddypress_messages_spamblocker_12h’)</li>
<li>Users can send 45 messages maximum in 24 hours (modify this value using filter ‘buddypress_messages_spamblocker_24h’)</li>
<li>Users can send 50 messages maximum in 48 hours (modify this value using filter ‘buddypress_messages_spamblocker_48h’)</li>
</ul>
Users with the capability “edit_users” (admins etc.) have no restrictions for outgoing messages
Install, activate, and it will work.
More about me and my plugins
Since the year 1999 I do administration, customizing and programming for several forums, communities and social networks. In the year 2013 I switched from another PHP framework to WordPress. 
Because not all plugins I’d like to have exist already I wrote some own plugins and I think I’ll continue to do so.
If you have the scope at forums or social networks my other modules might also be interesting for you. <a href="https://wordpress.org/plugins/search.php?q=quan_flo" title="ifs-net / quan_flo WordPress Plugins" rel="ugc">Just take a look at my WordPress Profile to see all my Plugins.</a> Use them and if my work helps you to save time, earn money or just makes you happy feel free to donate – Thanks. The donation link can be found at the right sidebar next to this text.

Buddypress Messages Spam Blocker

This plugin will block mass mailing for the buddypress messaging system

Tom Anbinder

Pablo Pacheco

WPFactory

Kousik Mukherjee

Omar AlDabbas

Algoritmika

Thanks to IT

The Cart & Checkout Notices/Messages for WooCommerce plugin lets you add and customize cart and checkout notices in WooCommerce.
Enhance your WooCommerce store’s communication with the “Cart & Checkout Notices/Messages for WooCommerce” plugin, a tool designed to help you add and personalize notices on cart and checkout pages.
This plugin facilitates a richer shopping experience, allowing you to add custom messages to guide, inform, or update customers as they shop. Whether it is to encourage additional purchases, offer discounts, or provide information about shipping policies; a well-placed notice can make a world of difference.
With the option to leverage the plugin’s shortcodes in your notices, you can even display dynamic information such as the current cart total. This feature opens up possibilities for a wide range of creative and helpful notices, giving you the ability to craft messages that resonate with your customers and enhance their shopping experience.
You can add an unlimited number of notices, giving you a robust tool to engage with your customers dynamically.
Don’t just stop at the basic notifications; unlock a plethora of opportunities to connect and communicate more effectively, fostering a responsive and informed shopping environment.
<h3>✅ Main Features</h3>
<ul>
<li>Add custom notices to the cart page.</li>
<li>Add custom notices to the checkout page.</li>
<li>Customize add to cart notices.</li>
<li>Use the plugin’s shortcodes in notices. For example, display the current cart total.</li>
<li>And more…</li>
</ul>
<h3>🗘 Feedback</h3>
<ul>
<li>We are open to your suggestions and feedback. Thank you for using or trying out one of our plugins!</li>
<li>Head to the plugin <a href="https://github.com/thanks-to-it/cart-messages-for-woocommerce" rel="nofollow ugc">GitHub Repository</a> to find out how you can pitch in.</li>
</ul>
<h3>ℹ More</h3>
<ul>
<li>The plugin is “High-Performance Order Storage (HPOS)” compatible.</li>
</ul>

Cart & Checkout Notices/Messages for WooCommerce

Add and customize WooCommerce cart and checkout notices.

Buddypress Messages Spam Blocker vs Cart & Checkout Notices/Messages for WooCommerce