Forums mIRC Help DCC living it's own fantasy.

The DCC send protocol sends the file size in bytes as a 32bit integer, and that gives a maximum size of 2^32 bytes = 4GB. DCC was never intended for sending such large files.

I suggest using a protocol more suitable to file transfer, like FTP (file transfer protocol). It might be a good idea to keep your files below 2GB too, most compression tools allow to create multiple volumes.