Emailing your boss when you get sick can be rather daunting. The best thing to do is to keep the email brief, and highlight the most important information.
- What illness you're sick with
- How long you expect to be sick for
- Things that will remain unattended in your absence, that need looking after
- The best way to contact you in case of emergencies or problems.
- Reiterate the exact date you expect to be back by (this makes a good reference for your boss should he want to look up the day from his inbox)
Like I mentioned earlier, when emailing a boss about sick leave you want to keep it fairly brief. The last thing you want to do is clog up your boss's inbox with a long essay about your latest illness.
Instead, keep it to-the-point and professional, and you shouldn't have any problems!