It is impossible, when you try to send bitcoins to another address, and you suddenly have a typo mistake, the wallet provider is going to show you that address as a wrong one.

That is why it is almost impossible to have that kind of mistake, because the transactions that have been sent to wrong addreses are never sent.

Probably, there is one chance in one hundred to send bitcoins to another address that already exists.

maybe the addres is xxxxxxxxxxxx1, and you change that 1 to 2, and it can send it, but it is just that, one chance in a hundred.