We ran into a problem with a not so sophisticated email client which had to pull messages via IMAP from our GroupWise system. The emails were tagged with the strikeout markup in the mailbox and the email client downloaded these messages with every connection to the GWIA. The email client doesn't have a setting like Move deleted messages into trash.
Since SP1 of GroupWise 8, there is a nice new feature in the Client Options of user accounts (or at postoffice or domain level) to move items with the strikeout markup instead of ignoring them. You can activate this by opening ConsoleOne, open a user account in the GroupWise View, go to Client Options and check the box IMAP copy results in a GroupWise move under the General tab.
This works great for basic GroupWise systems. However, more experienced and responsible admins have a backup solution for GroupWise which uses the Smartpurge feature.
Smartpurge allows the administrator to disable purge operations of users before GroupWise messages are backed up. Only if a backup job has run successfully, a user can purge messages out of the GroupWise system.
If this feature is enabled, we run into the problem I described at the beginning. The IMAP client wants to delete a message which it has pulled, but because of the Smartpurge feature, it is only tagged with the strikeout markup and pulled again and again.
To avoid this, we have to disable Smartpurge. You go again into the Client Options like mentioned before. Under the Cleanup tab, you can uncheck Do not purge items until they are backed up and voila, everything works like it should.