how to build a mass mail address file

agporte wrote:

what are the steps to load addresses to mass mail file?

You have not provided much detail or context about what it is you want to do.

You could make a contact list in your email client. Or, you could keep a list of email addresses in a database or spreadsheet.

What are you trying to accomplish. If the goal is to send mass emails, your email service provider may restrict sending mass emails.