How can I send emails to more the one email address
Use your mailing program. This is simpler, more versatile and more powerful.
For more advice, mention your OS nme, LO version, save format and mailing program.
Your mailer is accessed from a web browser. Usually this can’t be scripted. In other words, LO may eventually launch your web browser but is unable to direct it to the webmail URL. Sending through webmail is a manual task, i.e. open first the webmail service, create a message and attach the LO document.
If your mail service is reached through a mailer program such as Thunderbird, Outlook, … LO can create the message outline. You “only” have to add recipients.