Interfering with the royal mail has long been considered offensive. there is no reason why the new mail, electronic communications, should not be subject to the same protections. Privacy in private, personal communications should not be undermined just because its easy to do so.
My ISP has aadmitted to retaining my emails from as far back as 2001, claiing that the law requires them to do so. It felt as though I had just discovered that the post office had been photocopying all my mail n case the state later wanted to read it.
Any such laws should not only be repealed, but data protection laws strengthened to prevent providers from retaining details of private emails.