‘Old’ KB article, but still current: After the upgrade to R2 the Console shows customized subscriptions

When having upgraded from OpsMgr SP1 to R2 the Console might show customized subscriptions with a name like ‘SMTP{GUID}’. For instance: ‘Smtp246f401e_1325_23a5_5631_ad173ff12532’.

Even though KB article KB971233 dates from May 2009, it is still current. It describes this issue and how to solve it.