• Click the Tools menu, and then click Split.
• In the Mailing List Utility window, click Browse button to locate the mailing list file you would like to split.
• Enter the number of email addresses per file, and the Base Name of the output file
• Click Start to begin split process

Mail Communicator will generate output mailing list files using Base Name provided followed by an increasing number.
By default the output file Base Name is "spliter", as a result Mail Communicator will generate the following files: "spliter1.txt", "spliter2.txt", "spliter3.txt" ... and so forth.
Nevertheless you may use a different Base Name if you wish.