Procedure to join Google Groups without creating a Google account:
1) First send an email to (Group Name)+email@example.com.
2) +subscribe is the key, which is appended to the end of group’s email address.
3) (Group Name) is the name of the group. Space is substituted by “-” (hyphen).
4) Now send an email to firstname.lastname@example.org.
5) Visit he group web page on Google Groups, and click on “About this group”.
6) Now select “About” in the drop down menu.
7) Look for group email address in the heading of “Group email”, it will look like: Group email email@example.com.
Note: You should send the subscribing email from the email address which you want to receive the messages mailing. You may need to confirm the subscription request for some groups.