Hi Javier,

The attachments are encoded before they are send. The different methods used to do that known as "Quoted-Printable", "Base64", UUENCODE, e.t.c. Encoding increases the size of attachment by 25%-35%. To show progress you don't need exact size, so following formula should work for you.

EmailSize = (BodySize + AttachmentSize) * 1.35

>I want to show a progress bar when sending a message. I use SEE DLL which tells me the total bytes sent, but I need to know in advance the size of the message including attachments. Is there any way to calculate it?