Without knowing exactly what has happened, in conjunction with the other thread you posted today I think you're having trouble due to file corruption caused by the power outage hitting your computer at the worst possible time.
My advice would be to revert to a backup copy of the file (if you have one). Failing that, rebuilding from scratch is the preferred process for ensuring no corruption exists in a file.
If you're happy to keep using the file in its current state, I would see what happens when you reset each and every piece of information in that particular script step, and if that doesn't work, create a new Send Email step in that script and populate it with the appropriate data, and if that doesn't fix it, re-create the entire script.
This might sound like a lot of work, but dealing with file corruption is. You can test every object you can think of and recreate things to the nth degree and there _still_ might be something wrecked in the file and you can never find it or access it. In the future, keep good backups and test hem occasionally so you know which ones you can trust.