I tried to send mail to a Google Group I am a member of, and receive the following error message back from Google:
- Google Groups
- MIT Google Apps at http://www.google.com/a/mit.edu
If you are certain that you sent mail to a valid group, then there could be two reasons for the above error:
The group allows only members to send mail to it, and you are not a member. You need to join the group before you can post to it. You can browse for the group at http://www.google.com/groups and submit a request to join the group (if it is restricted) from the group's web page.
If you are a member of the group and you just started getting an error like the above on posting around Sep. 4th, it is possible that your member email address was changed to firstname.lastname@example.org when Google merged MIT Google Apps accounts into their general Google account infrastructure. This would only have happened if you registered yourself for an MIT Google Apps account on the old "Teams Edition" Google was running.
for more details of this issue, work-arounds, and the recommended long-term fix.