This problem occurs because the Sniffer Installer cannot find the registry keys for MDaemon on a 64-bit installation. You can still use Message Sniffer by configuring MDaemon to call Message Sniffer using the Content Filter.

1.) Download the Message Sniffer for Windows from here.
2.) When installing Sniffer, choose "Other" as the platform and install it to something such as D:\SNF Create the following Content Filter Rules:

a. 'SPAM: Run Message Sniffer'
i. Apply this rule to messages in the LOCAL & REMOTE queue
ii. Select Condition: 'All Messages'
iii. Select Action: 'Run Process...'
Program to execute: Enter the full path and command to run Message Sniffer. Replace the file name with '$MESSAGEFILENAME$' (must be all caps and enclosed by quotes) i.e.
D:\SNF\SNFClient.exe '$MESSAGEFILENAME$'
Seconds: Set to
Force to terminate: Unchecked

b. 'SPAM: Add Headers'
i. Apply this rule to messages in the LOCAL & REMOTE queue
ii. Select Condition: 'All Messages'
iii. Select Action: 'Add Extra Header Item 1 To Message'
Header Name: X-SPAM-Message-ID
Header Value: $MESSAGEFILENAME$ (must be all caps)
iv. Select Action: 'Search And Replace Words In A Header'
In The ... Header: X-SPAM-Message-ID Search Expression: Your MDaemon Dir (i.e. 'D:\Mdaemon\') Replace With: Leave Blank (Will Remove the Text)
v. Select Action: 'Add Extra Header Item 2 To Message'
Header Name: X-SPAM-Msg-Sniffer-Result
Header Value: $EXITCODE$ (must be all caps)

c. 'SPAM: White List' (This rule will vary)
i. Apply this rule to messages in the LOCAL & REMOTE queue
ii. Select Conditions: 'If The FROM HEADER Contains'
Check For This String: Add Names of senders that you want excluded from SPAM Rules.
iii. Select Action: 'Skip n Rules'
Skip Over How Many Rules: 1

d. 'SPAM: Disposition'
i. Apply this rule to messages in the LOCAL & REMOTE queue
ii. Select Conditions: 'If The User Defined HEADER Contains'
UserDefined Header: X-SPAM-Msg-Sniffer-Result Change 'Contains...' to 'Is Not Equal To...'
Check For this String: 0 (Zero)
iii. Select Action: 'Move Message To Public Folders...'
For this you can create/select a Public Folder 'SPAM'