The mail flow in a company often contains a lot of email duplicates: messages from external and internal senders are forwarded to colleagues, bosses and relevant departments. When you receive a letter and realize that it should have been addressed to a different employee of the company, you usually press Forward without any further delay. As soon as you have done so, there are at least two copies of the same message in your email database. This would not present a slightest problem, were it not about email attachments. Unless commanded otherwise, attached files are just dragged along with their messages, regardless of their size, file type and general relevance.