The same message can read as brusque or as fawning

Written formality does not translate cleanly, and the mismatch is invisible to the sender.

Written courtesy is calibrated differently in different places, and the calibration is invisible from inside it. A message that seems admirably efficient to the person who wrote it, direct, short, no wasted words, can arrive as curt and faintly cold. A message that seems properly respectful, with an unhurried opening, an enquiry after the reader's wellbeing and a carefully softened request, can arrive as excessive and even as slightly insincere. Neither writer has misjudged their own convention. They have simply used it on somebody working from a different one.

What makes this harder than face to face greeting is that there is no feedback. Nobody replies to say that your opening felt abrupt. They reply a little more coolly, or a little later, or not at all, and the sender attributes the outcome to the content of the request rather than to its wrapping. Whole working relationships settle at a slightly lower temperature than either party intended, for reasons neither one can see, because both of them are behaving exactly as they were taught was polite.

There is no formula that fixes this, but there is a useful habit: read the reply for its shape as well as its content. If the answer that comes back is noticeably longer and warmer than what you sent, you have probably pitched below the reader's norm. If it is markedly shorter and plainer, you have probably pitched above it. Neither is a rebuke. It is the only signal available, it arrives free with every exchange, and almost nobody reads it.