In many cultures it is considered polite to wish people well on religious holidays (e.g. Christmas, Ramadan, Diwali). I often receive (Christmas) seasons greetings from various (usually US based) services. While I don't find this offensive, I can imagine some people finding it so.
What if anything should we do over religious holidays to be polite and respectful of peoples beliefs while still not alienating others?
Edit: to clarify, I'm speaking specifically about companies doing things like sending emails or putting something on their website. Not general issues of how people treat each other.