How do you say welcome in a message?

Excuse me, could you please elaborate on how one might properly express a welcome sentiment within a message? I'm curious about the nuances and etiquette involved in crafting such a greeting, as I understand that different contexts may call for varying levels of formality or informality. Perhaps you could provide some examples of welcome messages tailored to specific scenarios, such as for a business email, a personal chat, or a greeting at the start of a virtual meeting. It would be greatly appreciated.