The very large volume of mail to lists yesterday resulted in significant delivery delays up to 4 hours in some cases. CUIT staff are studying performance to determine causes and means to avoid the same in the future.
The MX records for 115 domains handled by CUIT now direct mail into the new linux incoming mail servers. Most of these are subdomains of columbia.edu but a few are .org domains affiliated with the university.
Users do not need to do anything different. There was no downtime.