How about the common mistake of entering xyz@abc,com instead of .com. A lot of times I unintentionally make this mistake. If the system doesn't prompt me in thi

How about the common mistake of entering xyz@abc,com instead of .com. A lot of times I unintentionally make this mistake. If the system doesn't prompt me in this case then I would never know why I didn't receive any further communication from it. That's FAIL in my opinion.