To be honest, sending stuff by normal email, although in theory it's very easy to hack and read, is probably more secure than normal snail mail, especially bearing in mind that Royal Mail catch nearly 500 postal workers every year stealing mail, and lose 250,000 letters every week.
That's why I get annoyed with firms which insist on switching to secure email even for routine things - they're a real pain to access, and remember the login details and it drastically increases the time taken to get to the information.