You may send a simple message via SMS, WhatsApp, Social Media Messaging, etc. But emails are highly recommended, especially because besides the decision maker, you can officially include other applicable stakeholders using the “CC” (Copy) and “BCC” (Blind Copy) options. There are other interesting reasons to communicate with Clients via email, but I’ll touch on those in another article.
Remember to obtain confirmation as previously advised, because this will serve as a reference point if any stakeholder somehow misinterprets certain points. This principle may also be applied Clients or between colleagues and typically, confirmation should be done via the same medium of initial communication (e.g SMS, WhatsApp, Social Media Messaging, etc.). But of course, there are exceptions to every rule!