Many messages maybe being quarantined due to scan error as Malformed Container. This can cause a lot of messages to be quarantined that will have to be released.
In most cases the following two parameters are all that is needed. Add the following lines to your notes.ini file:
SAVMalformityDetection=0
SAVExtendedMalformityDetection=0
Also, if you get Malformed Container errors from messages in MIME format via SMTP you can also add the following line to your notes.ini:
SAVMimeIdStrength=0