DCC Send allows you to send a file to another user. You can do this by clicking on the DCC Send toolbar button to open the DCC Send dialog. You can then enter the nickname of the user, select the file you want to send, and click on the Send button.
mIRC will then tell the user that you want to send them a file. The user then has to accept your send request, at which point the file transfer will begin.
The packet size is the number of bytes that mIRC will send to another client in one packet. The minimum is 512, the maximum is 8192.
If you check minimize then the dcc send window(s) will be minimized automatically.
The fill spaces option replaces spaces in long filenames with an underscore character. For more information read this.
Turning on this option should speed up your DCC sessions. You can also change this setting with the /fsend [on|off] command.
Note: DCC Send needs to use your IP address to initiate a connection with another client. If you are having trouble initiating a connection then your IP address might be wrong. See the Local Info section for more information.
i don't find where to "check" the minimize , i only found for on get only