@Velizar if you just wanna try to test the port connectivity,you can try modifying the port number of the server in the eNSP by double click the server icon in the topology.Or if you wanna test whole function of mail server,I'm sorry to tell you,it's not supported, maybe, you can try add a cloud and implement a mail server on your own PC,and connect you mail server through cloud. hope this can help you!
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