Before gifting a foreign colleague, check 3 common cultural pitfalls that could turn it into an insult.

Before a joke or offhand remark about food/fasting/holidays, check the listener's religious considerations.

In every long message you reply to, quote the specific line/question to make the thread readable.

Explicitly state your expected response times (not instant) in your signature or status, protecting your time and ending "why hasn't he replied" anxiety.