Send email from Access Database

Hi Experts,
I have questions about send email from Access Database.  I have a form in Access Database for users to sent Attachments to people.  I have few questions.
1).  since not every one's email is in outlook, some of them are using yahoo or gmail or Hotmail.  what else I need to add to the code?
2). I want to add button that users can click on to open the path to attach file to send, I tried to add a command button but it doesn't work.
3). How do the recipient knows sender's email address?

This is the first time I tried to do this in Access.  I found this sample and tried it to see if it works.
attached is my form.

Any help will be appreciated, but if it can be done then that's ok, thanks for your time
Thanks,
frmEmail.mdb