Removing 'if possible' would make your request stronger, and could eliminate the need for 'at the latest.' Be careful doing this if you're writing a superior.

Additionally, you don't need to say 'today.' When you say 'by tomorrow at the latest' or 'no later than tomorrow,' it's understood that receiving it today is acceptable and ideal as well. It's good to keep email word and character counts low.

Removing if possible would make your request stronger, and could eliminate the need for at the latest. Be careful doing this if you're writing a superior.

Additionally, you don't need to say today. When you say by tomorrow at the latest or no later than tomorrow, it's understood that receiving it today is acceptable and ideal as well.