Please note that I am back to the office on April 10, 2011 after my emergency leave on March 29, 2011. /
Please note that I am returned to the office on April 10, 2011 after my emergency leave on March 29, 2011.
Please note that I am back to the office on April 10, 2011 after my emergency leave on March 29, 2011. /
Please note that I am returned to the office on April 10, 2011 after my emergency leave on March 29, 2011.
"Please note that I am back at/in the office..." or "Please note that I was back at/in the office..." if we are talking about the past.