In reality, there is no such thing as an "official sick leave email" that covers all companies, eventualities, and illnesses.
The letter you will need to submit will vary from employer to employer, and the standard of proof may be dependant on factors like your sick leave history, how strict your work environment is, or even what kind of illness you are suffering from.
However there are several things it's worth knowing about when writing a sick leave email:
What you need to know about sick leave emails
1. Keep it formal. Not matter how relaxed your workplace is, a sick leave request will probably go on your file, so treat it as an important document.
Start with something like:
To Whoever it may concern,
I regret to inform you that I have been taken ill unexpectedly, and kindly request that you afford me a leave of absence to recuperate.
2. Your boss will always be skeptical.
Unless you're one of those lucky people that work in a mega-trusting work environment, your boss will want to know every detail about your absence. So make sure your email covers all the key aspects, such as length of absence, reason for absence, expected return date.
3. Provide evidence when possible. Just like school, you may need a doctor's note. I'd recommend not faking it, incase you get caught out!
4. Always make it look like you are going out of your way to return to work as soon as possible.
Say things like, I am truly sorry for any inconvenience this has caused, and I am eager to return to work as soon as I have recovered.