What to include
The address of the site, what is happening, and roughly when it started. If there is an error message, paste it in. If something was deployed or updated just before it began, that is usually the answer.
Response time
Every enquiry gets a reply within one working day, including the ones I turn down. If the site is fully down, say so in the first line and it goes to the top.
Working across time zones
The working day here overlaps the whole UK and Nordic day and the North American morning. Work outside those hours is arranged in advance rather than assumed. Say what suits you and it will be accommodated where it can be.