The primary mail server, elephant.ru.ac.za, has run out of disk space on one of its partions. While this has no direct impact on people's e-mail, as the partion holds all the authentication information for the mail and proxy servers, it means the services provided by elephant are likely to be unstable until the problem is resolved. This is, unfortunately, going to take several hours and will likely be done after hours during the course of this week.
In the mean time, a temporary workaround has been put in place that'll ensure that users are still able to access the mail server. This involved moving some less critical files around to free up disk space on the partition concerned.
More details, such as the date and time work is likely to commence, will be posted here once they're known.