The University currently allows unencrypted (unsecured) connections to its IMAP mailbox servers. Such connections are not secure, and have been informally deprecated for some time. Support for unencrypted clients was retained to reduce the disruption for people with older mail clients, and the intent was that over time natural attrition would remove the need for this.
Unfortunately we continue to see new email clients configured to use unsecured connections to the IMAP servers. For this reason, we will be discontinuing support for unencrypted IMAP connections at the end of June 2015.
You do not need to do anything about this immediately; if your computer is scheduled to be upgraded or replaced at the beginning of 2015, that would be an appropriate time to make this change. However, from July next year, any email client that does not make use of an encrypted IMAP connection will not be able to access mail.
The same will apply to unencrypted POP3 connections. However, rather than using encrypted POP3, users are strongly encouraged to move to IMAP. The use of POP3 is not supported, and the service is provided as-is.
If you'd like to check your mail settings, information on correctly configuring most mail clients can be found at http://www.ru.ac.za/static/it/configs/. There are also generic instructions showing the correct settings for any client.