How do you say you're welcome in a message?

Can you explain to me, in detail, how one might express their gratitude in a message, particularly by saying "you're welcome"? Is there a specific phrase or tone that is considered most appropriate? How does the context of the message impact the choice of words? Is there a cultural nuance that I should be aware of when saying "you're welcome" in a message? I'm interested in learning more about the etiquette and customs surrounding this common phrase.