I'm using Comcastbiz.com as my mail server and looking at Thunderbird as a possible mail client because Comcast's mail client leaves a lot to be desired. I already reset the POP3 & SMTP server addresses. I've been trying test e-mails. I clicked and dragged 16.5 meg worth of pictures into the body of the e-mail with no text and went to send it to myself. I clicked send and it told me that I was about to send a 20.5 meg e-mail. I clicked cancel and checked the size of the pics I was sending, 16.5 meg like I said. I went to resend and it then said I was about to send a 20.2 meg e-mail. Do I have to automatically add another 4 meg to the size of my e-mails for some reason, or is this not accurate? (20.5 one time, 20.2 the next time, accuracy seems to be suspect) Thanks

   Someone Already explain about it so go on below link: