We run a list of our mailman listserver that our public school sysadmins use to share info. The problem is - a lot of them have become Google schools, and Google has a problem with list servers.
Each post winds up going to multiple Google mail domains, and they bounce:
stat=Deferred: 451-4.3.0 Multiple destination domains per transaction is unsupported.
meaning the emails are queued, sometimes for quite a while, as the system sends each domain, one attempt (and one mess of deferrals) at a time.
Is there a setting I can change or add that would allow mailman to kind of bundle each domain, open a thread, and send one-thread-per-domain or one-domain-per-thread to alleviate the issue?
We are a bit behind, using Mailman version: 2.1.20