I am not sure what do you want to accomplish exactly, but I assume that this is needed for users who do not use EPESI every day but still treat e-mail client as their CRM.
Let me put my 2 cents here:
It would be much easier - from operational point of view - to convince users to start using EPESI CRM for all tasks. Even if you prefer to use a desktop e-mail client (I personally use Postbox and EPESI/Roundcube) - you can still have 2 applications open on your computer: e-mail client and a browser with EPESI 🙂
This way switching to EPESI to see a Dashobard with applets like Agenda, Tasks and Phone calls etc. is much simpler than viewing an alert in your Inbox in the desktop e-mail client which is just a plain text. You still need to open EPESI to view details, change the status or attach a note.
Frankly I do not understand the concept of sending an alert via e-mail from a CRM application which should be the focal point of your work.
I understand however that for occasional users of CRM systems (someone who logs in few times a week or month) an alert via e-mail could be useful. We added this feature and probably some die-hard e-mail users utilize this function. This is completely against our philosophy (e-mail is dead because of SPAM and overuse) and we do not plan to spend our development time on this "e-mail alerts" idea.
Please feel free to modify the existing functionality - the module is located in: modules\Utils\Messenger
and adapt it to your needs. In that case you don't need to create a separate module - if changes you will make will be useful we will simply incorporate it in the future releases.