Email is fast, in fact it is virtually instantaneous if the computer is working.
However, email is not without problems. One issue is privacy. Although managers of computer systems and others are not supposed to read email, and will often claim it's impossible for them to read messages, you should never assume your messages are private. There are encryption programs available, but for every programmer writing an encryption routine, there are 1000 others writing routines to decode it. Government agencies such as the National Security Agency can probably decode pretty much everything.