i working on REM systems.
i am project manager.
info about REM is link google search etsi 102 640 .
part of Registired Electronik Mail are e-signature(CAdES-A,XAdES-A,PAdES-A,eMail Sign smime),postfix mta,dovecot mda,centos os,mysql(percona cluster db),glusterfs,HSM(Hardware Secure Modul),wso2 web servis , zenoss network monitoring program
REM Mail system like rpost system() in USA.
i know structure matecate translate open software.
i write extensions for chrome
i wrote php web site that send text,image,audio,video on whatsapp.
i can give you demo user info for test
i can send to your phone numbers (from cvs files,excel files )
your bulk message via whatsapp api.