During the outage, no incoming or outgoing mail will be processed. There will likely be delays in delivering mail as sending machines will wait some amount of time before retrying, but no email should be lost.
Mailing list owners may want to [browse the documentation](http://www.sympa.org/manual/index) to learn about the new features.
If this time is particularly bad for your group, please let us know as soon as possible by email to help@eecs.
UPDATE
[2015-08-19 21:18:57 | Rob McNicholas]
Some problem were encountered during the upgrade which have prevented it from being completed. Some software incompatibilities were encountered that could not be easily solved in the time frame allotted.
We have rolled back the changes and put the old server back into service for now. Due to the DNS changes that were made, the web interface will not be accessible until Thursday morning, but for now mail is being processed and delivered.
Resolved as of 2015-08-19 21:16:00