Would the install of Cyrus-Imap crash the standard sme application or?
Jesper,
The SME7 version of Cyrus-Imap will disable the "Standard" SME functions that it replaces. These is also an uninstall that will remove it & set things back as they were. So I believe it to be 'safe'.
Having said that, this isn't the most widely used contrib on SME and so there's no guarratees. I believe that the issues with the SME6 version that did cause problems when upgrading etc have been resolved, but as always, it may be different for you.