Email Sender Software for Mass Email Sending

Hello,
I have to send many Emails to a listed members. Think that my boss has given me a list. This list contains many Email id. I have to send a mail to every Email id. I am using gmail. I tried to use many softwares for this. But these softwares did not work properly. I want to get a free software that will work properly or is there any solution that can help me without using software? No confused answer please.
Thank you
