2011/07/07 - Problems saving sent messages to IMAP mailboxes
We are currently experiencing a problem with the IMAP mail servers which is preventing many mail clients from saving copies of sent messages in sent mail folders which are stored on the IMAP servers. We are currently working on a solution to this problem, and will update this post with more information when it is available.

A workaround to this problem is to set your mail client to save copies of sent messages in a local folder, rather than on the IMAP servers.
This problem is the result of incorrect information in our IMAP server software's documentation. We performed a partial upgrade that was supposed to be supported, and supposed to be completely transparent to IMAP clients. The intention was to complete the low-risk section first, and then extensively test the more complex work that had to happen subsequently.

However, the reality is somewhat different. We're now in a situation where two components are incompatible (despite the documentation indicating otherwise), which is leading to the problem with sent mail folders.

In order to resolve this we need to expedite the second part of the upgrade and get these two components back in sync. We're currently in the process of preparing a new storage server to do this.

Unfortunately the second part of the upgrade involves migrating mailboxes from one storage server to another. As soon as a particular user's mailbox is migrated, their sent mail folder should become accessible again. Because of the volume of mail involved (~ 3TB), this is likely to be time consuming. We're not able to predict how long the total process will take, or when individual users will be able to use their sent mail folders properly again.
We've implemented a temporary work-around for this problem which will allow people to use their sent mail folders whilst we work on the underlying problem.

To take advantage of this, you may need to either restart your computer or get it to flush its DNS cache. You can do the latter in Windows as follows:
go to the Start menu and select Programs / Accessories / Command Prompt. In the black command prompt window that appears, type
ipconfig /flushdns

and then press enter. You can then close the command prompt window.

(Note that your computer will automatically refresh the above settings by, at the latest, 11AM tomorrow morning, so this only applies during the course of today [and then only if you're still having problems with sent mail].)

Once you've done this, restart your e-mail client and things should work as expected.
An oversight in the implementation of the workaround described above will have meant that people wouldn't have been able to connect to the IMAP server from off-campus. This has now been fixed.
It seems that the webmail client at made assumptions about where the IMAP servers were located, and so continued to be affected by the sent-mail problem. This has been resolved.