WHAT HAPPENED?
TSO implemented a change to the CoC mailman service to address two issues that could cause some emails to bounce.

 
WHEN DID IT HAPPEN?
On Wednesday, November 5, 2014.

 
WHY DID IT HAPPEN?
TSO recently became aware of two issues that could cause mail being sent through mailman to bounce.  The first is a change that Google made to their spam processing.  Mailman in its default configuration sends email in batches, which is industry standard behavior for mailing lists.  However, in an effort to reduce spam, Google has begun filtering out those batched messages if they contain multiple domains in the same batch (e.g. gmail.com and a Google-hosted .edu domain).  The second is a limitation on the GTRI Exchange server for number of recipients in a single message.  As the list sizes have grown, some of them have begun to hit that size limitation, causing messages to bounce.

 
WHO WAS AFFECTED?
The bounce behavior only occurred under very specific conditions, but all CoC mailman list members were potentially affected.

 
WHAT DO YOU NEED TO DO?
No user action should be required, although mailman users may notice that email sent to large lists may take slightly longer to be delivered.  In addition, list members may also receive additional copies of emails sent to multiple lists if they're members of those lists.  TSO will reach out to list owners who have list members who were disabled or unsubscribed due to excessive bounces.

 
HAS THE PROBLEM BEEN RESOLVED?
Yes.  TSO implemented a change to mailman on November 5 to send individual messages instead of batched messages to address the two bounce situations detailed above.  Monitoring since then has shown this to have been effective at stopping these types of bounces, with the side effect that it can take longer for email to be sent to all list members and some members may now receive duplicate messages as detailed above.

 
WHO SHOULD YOU CONTACT FOR QUESTIONS?
TSO Help Desk (CCB 148, 404.894.7065, helpdesk@cc.gatech.edu).