excel file size differs from what outlook lists

[lethargos]

I sent an e-mail with an attached excel. The excel takes about 8MB and that's what it says next to the name of the excel, in Outlook. But in the mail list (in the sent folder) it says that the e-mail takes up 11MB. I'm using Outlook 2007. Any ideas where this difference comes from?

I don't even have any text written in the mail body. I only wrote a short text in the subject field.

 

[Ranger4]

This is caused by Attachment Bloat. This excerpt from an MS article explains it for you.

"Attachment bloat. When a file is attached to message, it has to be encoded. The encoding process causes attached files to become 1.37 times larger than they are on your computer. For example, if you send a 5 MB file attachment, the attachment is sent as 6.85 MB of data."