E-mails aren't a very good way of writing anything important. E-mails can get buried in the spam, e-mail addresses can change, people don't always check their email, people can adjust what they wrote retrospectively etc. Can't really beat snail mail for some things. (Though a cleft stick is better, I suppose, if slower.)

My understanding is that there's no legal requirement to get permission to perform or record stuff, as against the obligation there is to pay the appropriate royalties, and to make sure the relevant people are informed, so they can collect them. But Richard's right, you shouln't rely on folklore like that as a source of legal guidance.