Use Sendmail?

Then you need to check this out:

http://www.cert.org/advisories/CA-2002-28.html

A very good example why they supply MD5 Checksums. Many people fail to use them

As I understand it the checksum you describe refers to the actual file size that would show the code had been tampered with. Would you confirm this and for us not quite literate folks, would you kindly step by step? Do you just compare the file size?

The best way to describe MD5 check sum is to look at it as a digital figerprint MD5 or Message Digest can be used to create a unique value of a file, directory or whole drive. Try it on a file you have. do a

You will get a value something like this

It is arguably impossible for two files to have the same value something like 1 in several billion. In computer forensics before they analyze a hard drive or any form of media they do a md5 of all the contents then they create a ghost image of the drive. They then make sure that the md5 of the ghost drive matches the suspect drive. They then work off the ghost image knowing it is 100% the same as the suspect drive. And they can testify beyond doubt that the data is unaltered. If you do a md5sum of an image and you flip one single bit the value will be completely different.

Now that thats somewhat clear when they create a file for distribution they do an md5 if someone changes the file it wont match the original distribution md5 so you would know it has been altered.

I hope I helped