Today I am back to work after having heavy surgery and a month of sick leave. I used to work with overseas colleagues and I'd like to inform them that I've come back to work. What is the best way to write this email?
I'd keep it short and professional - you're not using a social network, but there's nothing wrong with letting people know you're back and OK, especially if they already know you've been away for surgery. I'd write something like
This is just a quick note to say that I'm back at work as of today. I appreciated all the messages of support I received, and I'd like you to know my surgery and recovery went well.
If there's anything that came up in my absence that needs my attention then please let me know.
I wouldn't send it to the whole organisation or a large mailing list, limit it to people/teams you work with who have a business reason to know you're back, or who you're socially close to (but not so close that they already know from outside work).