This Thursday (June 11th, 2009) Yahoo! Groups will be undergoing maintenance. During this time 50% of groups will be unavailable for up to an hour. The outage is scheduled to begin some time between 2 and 3 pm PT (10-11 pm GMT).
While the maintenance is going on, all features of affected groups, including messages, photos, attachments, etc. will be completely unavailable. However, once the outage concludes, any messages that were posted to these groups via email during this downtime will be distributed.
For more information (or to comment), see this blog post:
Thanks, and our apologies for any inconvenience the downtime may cause.
P.S. Remember that neither commenting nor replying to this message will get you help for problems you are experiencing with your group. The ONLY way to get help from Yahoo! is to contact Customer Care: