Exchange attachment size

The problem could be two fold. Firstly dependant upon which ISP he is using to send or receive the 10MB file, there could be a size limitation for attachments received or sent. I.E. Yahoo's is somewhere around 2MB and Hotmail is 1.5MB.
You could also have an attachment size limit on your exchange server if he is unable to send a file of that size. You can change that in the properties of the IMS (Internet Mail Service) located in the connections tab. Go into General and you should see a radiobutton for Mail Size Limit. You have the option of setting it to unlimited but I am not sure I would recommend that. Make it reasonable but logical.
You may be receiving errors if you are trying to send to your EX2K server with a file size that is over the limit. The errors can generate NDR messages stating the mailbox cannot be found. This is a glitch in EX2K and to the best of my knowledge M$ is working on it.
Good luck!

Mail and FTP are 2 totally different functions.

The SMTP protocol is used for simple mail transfer.

That means, it was not designed to deliver large files. This has nothing to do with exchange per se. But with the underlying delivery mechanism.

You can easily send a 10 meg file to every recipient on the local exchange server. Because it does not use smtp there to transport it. It is all internal, and only 1 copy get's distributed.

But when exchange (or any mail server for tha matter) has to communicate with another mail server, the delivery mechanism (smtp) has a predifined chunk size that it can send/recieve.

Where FTP was developed for the sole purpose of transferring files. And FTP is it's own protocol. It is it's own delivery mechanism with it's own data channel. It's optimized for large file transfer.

With e-mail, the files have to be encoded into the e-mail package and delivered.

FTP just sends the file in binary mode, which just sends out sequential bits of data, and the ftp client/or server reassambles it on the other side.

There is also a default file size limit in exchange. I keep mine at 4 megs.

The answers above were excellent on this subject. We do not use Exchange and I can vouch for this being the case with other e-mail clients and servers as well.

:)