CMB can be perceived as rather neutral and polite, particularly when it is used in a friendly manner or accompanied by the context. It is not that formal as to write the entire phrase but fits well in most professional ways, including workplace messaging applications. The additions can rearrange the tone, such as addings such as ASAP or emojis- urgent forms can be more solid. On the whole, CMB is an acceptable and practical shorthand as long as it is done in a respectful manner and the individual should engage in a decent discussion upon receiving a call. Know more about cmb meaning in text