In the organizations in which I have worked, e-mail is significantly more secure than USPS mail or interoffice mail. And, IMO, that many hands on the mail makes it kind of easy for a confirmation to never make it to the intended recipient. So my vote would be for an e-mail confirmation. Regarding Email, let me restate. Email systems by there nature are relatively insecure.
Email is kept in areas that are meant to be accessed by a number of users.
Routing adds to this problem. I am not suggesting that companies should use UPS rather than Email, but is the user password is compromised, Email would likely be as well. The problem lies with Email administrators and smart engineers. So regular distribution needs to be accommodated anyway. In general my advise is let the employee decide.