Hello, this would be horrific (* sorry
Some customers use e-mail-addresses like myname.1 (e.g. at Gmail service) and Gmail (and other e-mail-services) do not distinguish between an e-mail-address wich is myname.1 and myname1 (this is fact). But most of the users dont know about this and both e-mail-addresses can be different people.
You can read about that fact in Gmail usage description. And i also tried this for my own with such a similar e-mail-address.
So this means, when a customer use such an e-mail-address, it can be also seen by the other Gmail user as it is delivered in his mailbox when he registered this before at Gmail (or also some other services).
Then a totally foreign person can see all the order details, address, maybe bank account or such things.