Note the 'Group email' line: rubyonrails-core@googlegroups.com
Append +subscribe to the address and send an email with the subject subscribe. Here, we would send that email to rubyonrails-core+subscribe@googlegroups.com.
You'll receive a mail from the group asking you to confirm your subscription. Just hit reply and send the email without modifying the subject field.
Directions
Quick & Easy
rubyonrails-core
GroupName
prepended to+subscribe@googlegroups.com
rubyonrails-core+subscribe@googlegroups.com
Likely more reliable
rubyonrails-core@googlegroups.com
+subscribe
to the address and send an email with the subject subscribe. Here, we would send that email torubyonrails-core+subscribe@googlegroups.com
.References